U.S. patent application number 13/389637 was filed with the patent office on 2012-08-02 for polyester film, and solar-cell back sheet and solar-cell using the same.
Invention is credited to Shigeru Aoyama, Tomohide Masuda, Atsushi Shiomi, Kozo Takahashi.
Application Number | 20120192944 13/389637 |
Document ID | / |
Family ID | 43732417 |
Filed Date | 2012-08-02 |
United States Patent
Application |
20120192944 |
Kind Code |
A1 |
Aoyama; Shigeru ; et
al. |
August 2, 2012 |
POLYESTER FILM, AND SOLAR-CELL BACK SHEET AND SOLAR-CELL USING THE
SAME
Abstract
A polyester film has a laminate structure including a polyester
layer (layer P1) containing a crystalline polyester and inorganic
particles and a polyester layer (layer P2) containing a crystalline
polyester, inorganic particles, and an antihydrolysis segment,
wherein the content (Wa2) of the inorganic particles in the layer
P2 is at least 10 mass % of the layer P2, the difference between
the content (Wa2) (mass %) of the inorganic particles in the layer
P2 and the content (Wa1) (mass %) of the inorganic particles in the
layer P1, Wa2-Wa1, is 5 to 25 mass %, and the content (Wb2) of the
antihydrolysis segment in the layer P2 is 0.02 to 1.5 mass % of the
layer P2.
Inventors: |
Aoyama; Shigeru; (Otsu,
JP) ; Shiomi; Atsushi; (Otsu, JP) ; Masuda;
Tomohide; (Otsu, JP) ; Takahashi; Kozo; (Otsu,
JP) |
Family ID: |
43732417 |
Appl. No.: |
13/389637 |
Filed: |
September 7, 2010 |
PCT Filed: |
September 7, 2010 |
PCT NO: |
PCT/JP2010/065294 |
371 Date: |
February 9, 2012 |
Current U.S.
Class: |
136/256 ;
428/213; 428/473.5; 428/480 |
Current CPC
Class: |
B32B 2307/3065 20130101;
B32B 27/20 20130101; B32B 2307/714 20130101; Y10T 428/2495
20150115; H01L 31/049 20141201; B32B 2307/71 20130101; B32B 27/18
20130101; Y02E 10/50 20130101; B32B 2457/12 20130101; Y10T
428/31786 20150401; Y10T 428/31721 20150401; B32B 2250/24 20130101;
B32B 27/36 20130101 |
Class at
Publication: |
136/256 ;
428/480; 428/213; 428/473.5 |
International
Class: |
H01L 31/0216 20060101
H01L031/0216; B32B 5/00 20060101 B32B005/00; B32B 5/02 20060101
B32B005/02; B32B 27/36 20060101 B32B027/36 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 11, 2009 |
JP |
2009-210128 |
Claims
1. A polyester film having a laminate structure comprising a
polyester layer (layer P1) containing a crystalline polyester and
inorganic particles and a polyester layer (layer P2) containing a
crystalline polyester, inorganic particles, and an antihydrolysis
segment, wherein content Wa2 of the inorganic particles in the
layer P2 is at least 10 mass % of the layer P2, a difference
between content Wa2 (mass %) of the inorganic particles in the
layer P2 and content Wa1 (mass %) of the inorganic particles in the
layer P1, Wa2-Wa1, is 5 to 25 mass %, and content Wb2 of the
antihydrolysis segment in the layer P2 is 0.02 to 1.5 mass % of the
layer P2.
2. The polyester film according to claim 1, wherein the content Wa1
of the inorganic particles in the layer P1 is 0.1 to 5 mass % of
the layer P1.
3. The polyester film according to claim 1, wherein the layer P1
further contains a antihydrolysis segment and the content Wb1 of
the antihydrolysis segment in the layer P1 is 0.01 to 1 mass % of
the layer P1.
4. The polyester film according to claim 1, wherein a ratio T1/T2
between the layer thickness T1 (.mu.m) of the layer P1 and layer
thickness T2 (.mu.m) of the layer P2 is 2 to 15.
5. The polyester film according to claim 1, wherein one outermost
layer of the polyester film is a layer P1 and an other outermost
layer of the polyester film is a layer P2.
6. The polyester film according to claim 1, wherein the
antihydrolysis segment contained in the layer P2 is a
polycarbodiimide-based compound.
7. The polyester film according to claim 3, wherein the
antihydrolysis segment contained in the layer P1 is a
polycarbodiimide-based compound.
8. A solar-cell back sheet comprising the polyester film according
to claim 1.
9. A solar-cell back sheet, wherein the polyester film according to
claim 1 is disposed at an outermost position.
10. The solar-cell back sheet according to claim 8, wherein at
least one outermost layer of the back sheet is a layer P2.
11. A solar-cell comprising the solar-cell back sheet according to
claim 8.
12. A solar-cell comprising the solar-cell back sheet according to
claim 9.
13. The solar-cell hack sheet according to claim 9, wherein at
least one outermost layer of the back sheet is a layer P2.
14. The polyester film according, to claim 2, wherein the layer P1
further contains a antihydrolysis segment and the content Wb1 of
the antihydrolysis segment in the layer P1 is 0.01 to 1 mass % of
the layer P1.
15. The polyester film according to claim 2, wherein a ratio T1/T2
between layer thickness T1 (.mu.m) of the layer P1 and layer
thickness T2 (.mu.m) of the layer P2 is 2 to 15.
16. The polyester film according to claim 3, wherein a ratio T1/T2
between layer thickness T1 (.mu.m) of the layer P1 and layer
thickness T2 (.mu.m) of the layer P2 is 2 to 15.
17. The polyester film according to claim 2, wherein one outermost
layer of the polyester film is a layer P1 and an other outermost
layer of the polyester film is a layer P2.
18. The polyester film according to claim 3, wherein one outermost
layer of the polyester film is a layer P1 and an other outermost
layer of the polyester film is a layer P2.
19. The polyester film according to claim 4, wherein one outermost
layer of the polyester film is a layer P1 and an other outermost
layer of the polyester film is a layer P2.
Description
RELATED APPLICATIONS
[0001] This is a .sctn.371 of International Application No.
PCT/JP2010/065294, with an international filing date of Sep. 7,
2010 (WO 2011/030745, published Mar. 17, 2011), which is based on
Japanese Patent Application No. 2009-210128, filed Sep. 11, 2009
(now Japanese Patent No. 4849189), the subject matter of which is
incorporated herein by reference.
TECHNICAL FIELD
[0002] This disclosure relates to a polyester film which can be
suitably used particularly as a solar-cell back sheet, and a
solar-cell back sheet and a solar-cell, which use the film.
BACKGROUND
[0003] A polyester (particularly, polyethylene terephthalate
(hereinafter, sometimes, referred to as PET),
poly(ethylene-2,6-naphthalenedicarboxilate), etc.) resin is
superior in mechanical properties, thermal properties, chemical
resistance, electrical properties and molding properties, and is
used in various applications. A polyester film prepared by forming
the polyester into a film, particularly, biaxially oriented
polyester film, is used as various industrial materials such as
copper clad laminate plates, solar-cell back sheets,
pressure-sensitive adhesive tapes, flexible printed boards,
membrane switches, sheet heating elements, electrical insulation
materials of a flat cable or the like, magnetic recording
materials, capacitor materials, packaging materials, automobile
materials, building materials, photographic applications, graphic
applications and heat-sensitive transfer applications because of
its mechanical properties and electrical properties.
[0004] Among these applications, in electrical insulation materials
(e.g., solar-cell back sheet, etc.), automobile materials and
building materials, which are used particularly outdoors, are often
used under severe environments in terms of temperature and humidity
for a long period. Since in a versatile polyester, its molecular
weight is decreased by hydrolysis and embrittlement proceeds to
cause mechanical properties to deteriorate, improvement of the
polyester, that is, improvement of the moisture-heat resistance, is
required. Moreover, in order to prevent the fire spread in the
occurrence of a fire disaster, the flame retardancy is
required.
[0005] Accordingly, various investigations have been made to
suppress the hydrolysis of polyester. For example, a technique, in
which an antihydrolysis segment such as epoxy-based compounds
(Japanese Unexamined Patent Publication No. 9-227767 and Japanese
Unexamined Patent Publication No. 2007-302878) or polycarbodiimides
(Published Japanese Translation No. 11-506487 of the PCT
Application, Japanese Unexamined Patent Publication No. 9-7423 and
Japanese Unexamined Patent Publication No. 2003-41030) is added to
improve the moisture-heat resistance of polyester, is investigated.
Further, with respect to a biaxially oriented polyester film, a
technique of improving the moisture-heat resistance by increasing
the inherent viscosity (IV) of the film and controlling the planar
orientation is investigated (Japanese Unexamined Patent Publication
No. 2007-70430).
[0006] On the other hand, it is desired to impart properties other
than the moisture-heat resistance (e.g., a sliding property,
ultraviolet light resistance, a reflecting property, etc.) to
increase performance for these applications. Thus, investigations
concerning mixing other component (e.g., inorganic particle, etc.)
to enhance the functions are made (e.g., Japanese Unexamined Patent
Publication No. 2003-155403, Japanese Unexamined Patent Publication
No. 2-163155, Japanese Unexamined Patent Publication No. 2-191638
and Japanese Unexamined Patent Publication No. 2006-270025).
[0007] However, when other components (e.g., ultraviolet absorber,
inorganic particles, etc.) are mixed to enhance the function of a
polyester film, particularly a polyester film containing an
ethylene terephthalate unit as a main constituent, degradation of a
resin proceeds due to hydrolysis in kneading, and the resulting
film exhibits the function of the added component, but there is a
problem that moisture-heat resistance is deteriorated.
[0008] Further, a problem that addition of the antihydrolysis
segment causes the reduction of the flame retardancy arises.
[0009] Accordingly, it could be helpful to provide a polyester film
which is superior in moisture-heat resistance, flame retardancy and
ultraviolet light resistance.
[0010] We thus provide a polyester film having a laminate structure
comprising a polyester layer (layer P1) containing a crystalline
polyester and inorganic particles and a polyester layer (layer P2)
containing a crystalline polyester, inorganic particles, and an
antihydrolysis segment, wherein the content Wa2 of the inorganic
particles in the layer P2 is at least 10 mass % of the layer P2,
the difference between the content Wa2 (mass %) of the inorganic
particles in the layer P2 and the content Wa1 (mass %) of the
inorganic particles in the layer P1, Wa2-Wa1, is 5 to 25 mass %,
and the content Wb2 of the antihydrolysis segment in the layer P2
is 0.02 to 1.5 mass % of the layer P2.
[0011] It is possible to provide a polyester film which satisfies
moisture-heat resistance, flame retardancy, and ultraviolet light
resistance over a long period. Moreover, it is possible to provide
a solar-cell back sheet which uses the polyester film and, hence,
has high durability; and a solar cell including the back sheet.
BRIEF DESCRIPTION OF THE DRAWN
[0012] FIG. 1 is a schematic sectional view of a solar-cell using
our polyester film.
DESCRIPTION OF REFERENCE SYMBOLS
[0013] 1: solar-cell back sheet [0014] 2: sealing, material [0015]
3: power generation element [0016] 4: transparent substrate
[0017] The polyester film needs to be a laminated film comprising a
polyester layer (layer P1) containing a crystalline polyester and
inorganic particles and a polyester layer (layer P2) containing a
crystalline polyester, inorganic particles, and an antihydrolysis
segment. The antihydrolysis segment referred to herein refers to a
compound which reacts and couples with a carboxyl terminal group of
the polyester to disappear the catalytic activity of a proton
originated from the carboxyl terminal group, and the detail of the
antihydrolysis segment will be described later.
[0018] The polyester film requires that the content Wa2 of the
inorganic particles in the layer P2 is at least 10 mass % of the
layer P2, the difference between the content Wa2 (mass %) of the
inorganic particles in the layer P2 and the content Wa1 (mass %) of
the inorganic particles in the layer P1, Wa2-Wa1, is 5 to 25 mass
%, and the content Wb2 of the antihydrolysis segment in the layer
P2 is 0.02 to 1.5 mass % of the layer P2.
[0019] By satisfying all of the above-mentioned requirements, it is
possible to provide a polyester film which satisfies moisture-heat
resistance, flame retardancy, and ultraviolet light resistance at a
high level over a long period.
[0020] Moreover, the polyester film can be a polyester film
excellent in the curling resistance even in the case of a structure
in which, of the layer P1 and the layer P2 composing the polyester
film, the first layer from one surface is a layer P1 and the first
layer from the other surface is a layer P2 (hereinafter, these
structures are referred to as an asymmetrical structure, in
addition, other layer may be composed of a plurality of layers),
for example, (i) a two-layer structure consisting of layer P1/layer
P2, (ii) a multilayer laminate structure of consisting of layer
P1/layer P2/ . . . /layer P2, (iii) a structure consisting of layer
P1/layer P2/another layer, or (iv) a structure consisting of
another layer/layer P1/layer P2, layer P1/another layer/layer P2,
for example, as described later. The reason for this will be
described in detail below.
[0021] In a polyester, a crystalline polyester and an amorphous
polyester are present, and in a common crystalline polyester, a
crystalline part and an amorphous part are present. When such a
crystalline polyester is stretched, a part (hereinafter, oriented
crystallized part) where the polyester is pseudo-crystallized by
orientation is generated in a part of the amorphous part, but all
of the amorphous part are not pseudo-crystallized. Here, the
amorphous part is said to have a lower density and a larger average
intermolecular distance than a crystallized part or an oriented
crystallized part. We investigated moisture-heat decomposition of
the polyester, and found out that when a polyester film is exposed
to a moisture-heat atmosphere, water content (moisture vapor)
passes through between molecules in the amorphous part, which is
low in a density, and permeated into the film, and plasticizes the
amorphous part to increase molecular movement, that a proton
originated from the carboxyl terminal group of the polyester acts
as a reaction catalyst and hydrolyzes the amorphous part in which
molecular movement increases, and further that if the polyester is
hydrolyzed to be low in a molecular weight, molecular movement is
further increased, and this progress is repeated to cause
embrittlement of the film to proceed, and ultimately the film is
fractured even by a slight impact.
[0022] Generally, the inorganic particles are added to the
polyester to increase the function of the polyester film, and in
this case, a technique of preparing a master batch containing a
high level of particles once, and then diluting the master batch is
used. However, since the polyester undergoes the heat history
higher than its melting point in preparing the master batch, the
degradation of the polyester occurs. Moreover, since the inorganic
particle inherently includes adsorbed water, in the polyester
containing inorganic particles, a hydrolysis reaction is
accelerated. These two phenomena are combined, and consequently the
moisture-heat resistance is significantly deteriorated. On the
other hand, it is conceivable that to improve the moisture-heat
resistance deteriorated due to such phenomena, the antihydrolysis
segment is added, but if the antihydrolysis segment is added
simply, the moisture-heat resistance is improved, but the flame
retardancy is deteriorated because the heat resistance of the
antihydrolysis segment is low.
[0023] On the other hand, in the polyester film, by containing 10
mass % or more of the inorganic particles in the layer P2, it
becomes possible to impart the characteristic based on the kind of
the inorganic particle to the polyester film. Further, by setting
the difference between the content Wa1 of the inorganic particles
in the layer P2 and the content Wa1 of the inorganic particles in
the layer P1, Wa2-Wa1, within the range of 5 to 25 mass %, that is,
by lowering the content of the inorganic particles in the layer P1
to a level lower than that in the layer P2, it becomes possible
that the layer P1 has higher moisture-heat resistance.
[0024] Further, by setting the content of the antihydrolysis
segment in the layer P2 within the range of 0.02 to 1.5 mass % of
the layer P2, the moisture-heat resistance of the layer P2 can be
improved without impairing the flame retardancy, and thereby, the
moisture-heat resistance of the whole film can be improved.
[0025] Further, generally, when the inorganic particles are added
to the crystalline polyester, the inorganic particle becomes a
nucleus and the crystallinity of the polyester becomes high.
Further, it is known that thereby, orientation properties at the
time of stretching increase. Therefore, when the film has an
asymmetrical structure comprising the layer P1 and the layer P2, in
which the content of the inorganic particles are significantly
different from each other, the crystallinity and the orientation
properties of the layer P1 differ from those of the layer P2, and
therefore the film may be largely curled with the layer containing
less inorganic particles being inner side at the time of undergoing
heat history during using the film. We found that it becomes
possible to lower the crystallinity of the polyester layer (layer
P2) when the polyester layer (layer P2) containing more inorganic
particles contains the antihydrolysis segment. Thereby, we found
that a polyester film having excellent curling resistance can be
formed even when the polyester film has an asymmetrical
structure.
[0026] Hereinafter, our films, back sheets and solar cells will be
described in detail by way of specific examples.
[0027] In the polyester film, a crystalline polyester is used for
the polyester layer P1 and the polyester layer P2. The
crystallinity referred to here specifically refers to a resin in
which a crystal melting heat .DELTA.Hm determined from a peak area
of a melt peak is 10 J/g or more in a differential scanning calory
measurement chart of 2nd Run, which is obtained by heating a resin
at a temperature rising rate of 20.degree. C./min from 25.degree.
C. to 300.degree. C. according to JIS K 7122 (1987) (1st Run),
maintaining the resin for 5 minutes in this state, then quenching
the resin to 25.degree. C. or less, and heating the resin at a
temperature rising rate of 20.degree. C./min from room temperature
to 300.degree. C. again. When a resin not having the crystallinity
is used, a sufficient oriented crystallized part cannot be formed
even though the resin is subjected to stretching or heat treatment,
and the resin becomes low in moisture-heat resistance. Further, the
resin tends to result in unfavorable results in terms of the heat
resistance, dimensional stability and ultraviolet light resistance
of a film.
[0028] The crystallinity of the crystalline polyester is preferably
higher, and the crystalline polyester having a crystal melting heat
of preferably 15 J/g or more, more preferably 20 J/g or more is
preferably employed. By using a resin having crystallinity, it
becomes possible to better enhance oriented crystallization by
stretching or heat treatment, and therefore a polyester film having
excellent mechanical strength and excellent dimensional stability
can be formed.
[0029] The crystalline polyester used in the polyester film is a
polyester including a dicarboxylic acid constituent and a diol
constituent. In addition, the term "constituent" refers to a
minimum unit which can be obtained by hydrolyzing a polyester.
[0030] Examples of a dicarboxylic acid constituent constituting
such a polyester include dicarboxylic acids, for example, aliphatic
dicarboxylic acids such as malonic acid, succinic acid, glutaric
acid, adipic acid, suberic acid, sebacic acid, dodecanedioic acid,
dimer acid, eicosanedioic acid, pimelic acid, azelaic acid, methyl
malonate and ethyl malonate; alicyclic dicarboxylic acids such as
adamantane dicarboxylic acid, norbornene dicarboxylic acid,
isosorbide, cyclohexanedicarboxylic acid and decalindicarboxylic
acid; and aromatic dicarboxylic acids such as terephthalic acid,
isophthalic acid, phthalic acid, 1,4-naphthalene dicarboxylic acid,
1,5-naphthalene dicarboxylic acid, 2,6-naphthalene dicarboxylic
acid, 1,8-naphthalene dicarboxylic acid, 4,4'-diphenyl dicarboxylic
acid, 4,4'-diphenylether dicarboxylic acid, sodium
5-sulfoisophthalate, phenyl indane dicarboxylic acid, anthracene
dicarboxylic acid, phenanthrene dicarboxylic acid and
9,9'-bis(4-carboxyphenyl)fluorenic acid, and ester derivatives
thereof, but the dicarboxylic acid constituent is not limited to
these. Further, addition products formed by adding oxyacids such as
l-lactide, d-lactide and hydroxybenzoate, and derivatives thereof,
or a string of oxyacids to the terminal of the carboxyl group of
the carboxylic acid constituent described above are also suitably
used. These may be used singly, or may be used in combination of
plural kinds as required.
[0031] Further, examples of a diol constituent constituting such a
polyester include aliphatic diols such as ethylene glycol,
1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,2-butanediol
and 1,3-butanediol; alicyclic diols such as cyclohexanedimethanol,
spiroglycol and isosorbide; and aromatic diols such as bisphenol A,
1,3-benzenedimethanol, 1,4-benzenedimethanol and
9,9-bis(4-hydroxyphenyl)fluorene, and a string of the
above-mentioned diols, but the diol constituent is not limited to
these. These may be used singly, or may be used in combination of
plural kinds as required.
[0032] Further, in the polyester film, a ratio of the aromatic
dicarboxylic acid constituent in the total dicarboxylic acid
constituent in the polyester in the layer P1 and/or the layer P2 is
preferably 90 to 100 mol %. The ratio of the aromatic dicarboxylic
acid constituent is more preferably 95 to 100 mol %. The ratio of
the aromatic dicarboxylic acid constituent is still more preferably
98 to 100 mol %, particularly preferably 99 to 100 mol %, and most
preferably 100 mol %, that is, it is preferred that all of the
dicarboxylic acid constituent is the aromatic carboxylic acid
constituent. When the ratio of the aromatic dicarboxylic acid
constituent is less than 90 mol %, the moisture-heat resistance and
the heat resistance may be deteriorated. In the polyester film, by
setting the ratio of the aromatic dicarboxylic acid constituent in
the total dicarboxylic acid constituent in the polyester in the
layer P1 and/or the layer P2 within the range of 90 mol % to 100
mol %, it is possible to satisfactorily combine the moisture-heat
resistance and the heat resistance.
[0033] In the polyester film, as a main repeating unit composed of
the dicarboxylic acid constituent and the diol constituent, which
predominantly compose the polyester in the layer P1 and/or the
layer P2, a unit comprising ethylene terephthalate,
ethylene-2,6-naphthalenedicarboxilate, propylene terephthalate,
butylene terephthalate, 1,4-cyclohexylenedimethylene terephthalate,
ethylene-2,6-naphthalenedicarboxilate, or a mixture thereof is
suitably employed. In addition, the main repeating unit referred to
herein refers to the above-mentioned repeating unit, a total ratio
of which is 70 mol % or more, more preferably 80 mol % or more, and
still more preferably 90 mol % or more of all repeating units in
the case of the polyester contained in the layer P1 and/or the
layer P2.
[0034] Moreover, the main repeating unit is preferably ethylene
terephthalate, ethylene-2,6-naphthalenedicarboxilate, and a mixture
thereof in that cost is low, polymerization is easy, and the heat
resistance is excellent. In this case, when ethylene terephthalate
is used more as the main repeating unit, a versatile film, which is
lower in cost and has moisture-heat resistance, can be prepared,
and when ethylene-2,6-naphthalenedicarboxilate is used more as the
main repeating unit, a film having more excellent moisture-heat
resistance can be formed.
[0035] In the polyester film, the number of the carboxyl terminal
groups of the polyester composing the layer P1 and/or the layer P2
is preferably 15 equivalents/t or less. The number of the terminal
groups is more preferably 13 equivalents/t or less, and still more
preferably 10 equivalents/t or less. When the number of the
terminal groups is more than 15 equivalents/t, the catalytic
activity of a proton originated from the carboxyl terminal group is
high even if the antihydrolysis segment is added and, therefore,
hydrolysis is accelerated and degradation proceeds, and to suppress
the catalytic activity, much antihydrolysis segment has to be
added. Hence, flame retardancy tends to be deteriorated. To adjust
the number of the carboxyl terminal groups in the polyester layer
P1 and/or the polyester layer P2 to 15 equivalents/t or less, a
method 1) in which an esterification reaction between the
dicarboxylic acid constituent and the dial constituent is
performed, and a reactant is discharged at the time when the
reactant reaches a predetermined melt viscosity through melt
polymerization, formed into a strand, and cut to form chips, and
then the chips are subjected to solid phase polymerization, or a
method 2) in which a buffer agent is added during the time between
the completion of an ester exchange reaction or an esterification
reaction and the initial stage of a polycondensation reaction
(inherent viscosity is less than 0.3), can be employed, and thereby
a polymerized resin having the number of the carboxyl terminal
groups of 20 equivalents/t or less, more preferably 18
equivalents/t or less and still more preferably 15 equivalents/t or
less is formed, and then the antihydrolysis segment is added in the
proportion described later.
[0036] In the polyester film, the inherent viscosity (IV) of the
polyester composing the polyester layer P1 and/or the layer P2 is
preferably 0.65 or more. The inherent viscosity of the polyester is
more preferably 0.68 or more, still more preferably 0.7 or more,
and particularly preferably 0.72 or more. When the IV is less than
0.65, the moisture-heat resistance or the mechanical properties may
not be achieved because of an excessively low molecular weight of
the polyester, or a thermal crystallization rate after hydrolysis
may be increased and become brittle because of an excessively low
entanglement between molecules. In the polyester film, by setting
the inherent viscosity (IV) of the polyester composing the
polyester layer P1 and/or the polyester layer P2 at 0.65 or more,
high moisture-heat resistance or high mechanical properties can be
achieved. In addition, an upper limit of the IV is not particularly
determined, but the IV is preferably 1.0 or less, and more
preferably 0.9 or less since if the IV is too high, a
polymerization time is lengthened and it is economically
disadvantageous, and melt extrusion becomes difficult.
[0037] In addition, to adjust the inherent viscosity of the
polyester in the polyester layer P1 and/or the polyester layer P2
to 0.65 or more, by a method 1) in which the polyester is
discharged at the time when the polyester reaches a predetermined
melt viscosity through melt polymerization, formed into a strand
and cut to form chips, or a method 2) in which the polyester is
formed into chips once at an inherent viscosity lower than the
target value and then the chips are subjected to solid phase
polymerization, a resin having an inherent viscosity of 0.7 or
more, more preferably 0.75 or more and still more preferably 0.78
or more is formed, and the resin is extruded at a temperature of a
polyester melting point plus 10.degree. C. to the melting point
plus 30.degree. C., more preferably the melting point plus
15.degree. C. to the melting point plus 25.degree. C. in a nitrogen
atmosphere to obtain a polyester having inherent viscosity of 0.65
or more. Of these methods, as the polymerization method of a
polyester, the method 2), in which the polyester is formed into
chips once at an inherent viscosity lower than the target value and
then the chips are subjected to solid phase polymerization, is
preferable in that thermal degradation of the polyester can be
suppressed and the number of the carboxyl terminal groups can be
reduced.
[0038] The layer P1 and the layer P2 of the polyester film contain
inorganic particles. The inorganic particle is used to impart a
function required depending on its object to the film. Examples of
the particles that may be suitably used include inorganic particles
having an ultraviolet-absorbing power, particles having a
refractive index highly different from that of the crystalline
polyester, a particle having electrical conductivity, and a
pigment, and thereby weatherability, optical properties, antistatic
properties, and color tone can be improved. In addition, the
particle refers to a particle having a volume average primary
particle diameter of 5 nm or more. In addition, unless otherwise
noted, a particle diameter refers to a primary particle diameter,
and a particle refers to a primary particle.
[0039] Further, the particles will be described in detail. Examples
of materials of the inorganic particles include metals such as
gold, silver, copper, platinum, palladium, rhenium, vanadium,
osmium, cobalt, iron, zinc, ruthenium, praseodymium, chromium,
nickel, aluminum, tin, zinc, titanium, tantalum, zirconium,
antimony, indium, yttrium, and lanthanum; metal oxides such as zinc
oxide, titanium oxide, cesium oxide, antimony oxide, tin oxide,
indium-tin oxide, yttrium oxide, lanthanum oxide, zirconium oxide,
aluminum oxide, and silicon oxide; metal fluorides such as lithium
fluoride, magnesium fluoride, aluminum fluoride, and cryolite;
metal phosphates such as calcium phosphate; carbonates such as
calcium carbonate; sulfates such as barium sulfate; talc and
kaolin, and carbon-based compounds such as carbon, fullerene,
carbon fiber and carbon nanotube.
[0040] When particles having an ultraviolet-absorbing power, for
example, inorganic particles of metal oxide such as titanium oxide,
zinc oxide, cerium oxide or the like, are used in view of frequent
outdoor use, the positive effect of maintaining mechanical strength
over a long period can be remarkably exhibited taking advantage of
ultraviolet light resistance by the particles. When it is desired
to provide a high reflection property, barium sulfate, calcium
carbonate or the like is suitably used as inorganic particles since
these are superior in an air bubble forming property through
stretching.
[0041] The polyester film requires that the content Wa2 of the
inorganic particles in the layer P2 is at least 10 mass % of the
layer P2. The content Wa2 is more preferably 10 to 25 mass %, still
more preferably 11 to 22 mass %, and particularly preferably 13 to
22 weight % of the layer P2. When the content of the particles is
less than 10 weight %, the sufficient effect of the particles is
not exhibited, and the ultraviolet light resistance is extremely
insufficient particularly in the case of the particle having an
ultraviolet-absorbing power and mechanical strength may be
deteriorated when used for a long period. In addition, the content
of the particles is more than 25 weight %, film forming properties
may be deteriorated, or the moisture-heat resistance of the
resulting film may be significantly deteriorated. Moreover, it is
not preferable because curling of the film may increase when this
film has an asymmetrical structure. In the polyester film, by
setting the content Wa2 of the inorganic particles in the layer P2
within the range of 10 to 25 mass % of the layer P2, it is possible
to exhibit the effect based on the addition of the particles
without deteriorating the moisture-heat resistance, and moreover,
it becomes possible to suppress curling when the polyester film has
an asymmetrical structure.
[0042] In the polyester film, the difference between the content
Wa2 of the inorganic particles in the layer P2 and the content Wa1
of the inorganic particles in the layer P1, Wa2-Wa1, is preferably
5 to 25 mass %. The difference between the content Wa2 and the
content Wa1 is more preferably 7 to 22 mass %, and still more
preferably 10 to 19 mass %. When the difference between Wa2 and Wa1
is less than 5 mass %, the effect of containing the inorganic
particles may be deteriorated because of too small Wa2, or the
moisture-heat resistance may be deteriorated because of too large
Wa1. Further, when the difference between Wa2 and Wa1 is 25 mass %
or more, the moisture-heat resistance may be deteriorated because
of too large Wa2. Moreover, it is not preferable because curling
may increase too much when this film has an asymmetrical structure.
In the polyester film, by setting the difference between the
content Wa2 of the inorganic particles in the layer P2 and the
content Wa1 of the inorganic particles in the layer P1, Wa2-Wa1,
within the range of 5 to 25 mass %, it is possible to exhibit the
maximum effect based on containing the inorganic particles without
deteriorating the moisture-heat resistance. Moreover, even when the
polyester film has an asymmetrical structure, the film can be
excellent in curling resistance.
[0043] In the polyester film, the content Wa1 of the inorganic
particles in the layer P1 is preferably 0.1 to 5 mass % of the
layer P1. By setting the content Wa1 within this range, it is
possible to sufficiently exhibit the characteristic-improving
effect based on the addition of the inorganic particles without
deteriorating the moisture-heat resistance, and without
deteriorating the adhesion even when the film has an asymmetrical
structure and the surface on the layer P1 side is used as a close
contact surface. The content Wa1 is more preferably 0.5 to 3 mass
%, and still more preferably 1 to 3 mass %. When the content Wa1 of
the inorganic particles contained in the layer P1 is less than 0.1
mass %, the sufficient effect based on containing the inorganic
particles is not exhibited, and the ultraviolet light resistance is
significantly insufficient particularly in the case of the particle
having an ultraviolet-absorbing power and mechanical strength may
be deteriorated when used for a long period. Further, it is not
preferable because curling of the film may increase when the
polyester film has an asymmetrical structure. Further, when the
content Wa1 of the inorganic particles contained in the layer P1 is
more than 5 mass %, it is not preferable because the moisture-heat
resistance of the film may be significantly deteriorated, or the
adhesion may be significantly deteriorated when the polyester film
has an asymmetrical structure and the surface of the polyester
layer P1 is used as an adhesive surface. In the polyester film, by
setting the content Wa1 of the inorganic particles in the layer P1
within the range of 0.1 to 5 mass % of the layer P1, it is possible
to exhibit the maximum effect based on containing the inorganic
particles without deteriorating the moisture-heat resistance, and
moreover, it becomes possible to satisfactorily combine the
adhesion and curling even when the polyester film has an
asymmetrical structure.
[0044] In the polyester film, the content Wa of the inorganic
particles in the whole film is preferably 1.5 to 9 mass %. The
content Wa of the inorganic particles is more preferably 2 to 9
mass %, and more preferably 2 to 9 mass %. Further, when the
content Wa is less than 1.5 mass %, the sufficient effect based on
the addition of the particles may not be exhibited. Further, when
Wb is more than 9 mass %, the moisture-heat resistance of the film
may be deteriorated. In the polyester film, by setting the content
Wa of the inorganic particles in the whole film within the range of
1.5 to 9 mass %, it is possible to exhibit the maximum effect based
on containing the inorganic particles without deteriorating the
moisture-heat resistance. An average particle of the inorganic
particles used in the polyester film is preferably 0.005 to 5
.mu.m, more preferably 0.01 to 3 .mu.m, and particularly preferably
0.015 to 2 .mu.m.
[0045] The antihydrolysis segment refers to a compound which reacts
and couples with a carboxyl terminal group of the polyester to
disappear the catalytic activity of a proton originated from the
carboxyl terminal group, and specific examples of the compound
include compounds having a substituent such as an oxazoline group,
an epoxy group, or a carbodiimide group.
[0046] The carbodiimide compound having a carbodiimide group
includes monofunctional carbodiimide and polyfunctional
carbodiimide, and examples of the monofunctional carbodiimide
include dicyclohexylcarbodiimide, diisopropylcarbodiimide,
dimethylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide,
tert-butylisopropylcarbodiimide, diphenylcarbodiimide,
di-tert-butylcarbodiimide, and di-.beta.-naphthylcarbodiimide.
Particularly preferable monofunctional carbodiimide is
dicyclohexylcarbodiimide and diisopropylcarbodiimide. As the
polyfunctional carbodiimide, carbodiimides with a polymerization
degree of 3 to 15 are preferable. Specific examples thereof include
1,5-naphthalene carbodiimide, 4,4'-diphenylmethane carbodiimide,
diphenyldimethylmethane carbodiimide, 1,3-phenylene carbodiimide,
1,4-phenylene diisocyanate, 2,4-tolylene carbodiimide, 2,6-tolylene
carbodiimide, a mixture composed of 2,4-tolylene carbodiimide and
2,6-tolylene carbodiimide, hexamethylene carbodiimide,
cyclohexane-1,4-carbodiimide, xylylene carbodiimide, isophorone
carbodiimide, isophorone carbodiimide,
dicyclohexylmethane-4,4'-carbodiimide, methylcyclohexane
carbodiimide, tetramethylxylylene carbodiimide,
2,6-diisopropylphenylcarbodiimide and
1,3,5-triisopropylbenzene-2,4-carbodiimide. Further, with respect
to polyfunctional carbodiimide, "CARBODILITE" LA-1 produced by
Nisshinbo Holdings Inc. as an aliphatic polycarbodiimide-based
compound, and "Stabaxol" P100 and "Stabaxol" P400 produced by Rhein
Chemie Rheinau GmbH as an aromatic polycarbodiimide-based compound
are suitably used.
[0047] Since the carbodiimide compound generates an
isocyanate-based gas through thermal decomposition, a highly
heat-resistant carbodiimide compound is preferable. To enhance heat
resistance, a carbodiimide compound having a higher molecular
weight (higher polymerization degree) is preferable, and it is more
preferable that a terminal of the carbodiimide compound has a
highly heat-resistant structure. Further, once thermal
decomposition of the carbodiimide compound occurs, further thermal
decomposition tends to occur, and therefore it is necessary to
device a method of preventing the thermal decomposition, for
example, an extrusion temperature of the polyester is lowered as
far as possible. Aromatic polycarbodiimide-based compounds are more
preferable in that the moisture-heat resistance is higher, and for
example, "Stabaxol" P400 produced by Rhein Chemie Rheinau GmbH is
more preferably used in that the moisture-heat resistance is
high.
[0048] Further, preferable examples of the epoxy-based compounds
having an epoxy group include glycidyl ester compounds and glycidyl
ether compounds. Specific examples of the glycidyl ester compounds
include glycidyl benzoate, glycidyl t-Bu-benzoate, glycidyl
p-toluate, glycidyl(cyclohexanecarboxylate), glycidyl pelargonate,
glycidyl stearate, glycidyl laurate, glycidyl palmitate, glycidyl
behenate, glycidyl versatate ester, glycidyl oleate, glycidyl
linoleate, glycidyl linolenate, glycidyl behenolate, glycidyl
stearolate, diglycidyl terephthalate, diglycidyl isophthalate,
diglycidyl phthalate, diglycidyl naphthalene dicarboxylate,
diglycidyl(methyl terephthalate), diglycidyl hexahydrophthalate,
diglycidyl tetrahydrophthalate, diglycidyl(cyclohexane
dicarboxylate), diglycidyl adipate, diglycidyl succinate,
diglycidyl sebacate, diglycidyl dodecane diolate,
diglycidyl(octadecane dicarboxylate), triglycidyl trimellitate and
tetraglycidyl pyromellitate, and these can be used alone or in
combination of two kinds or more. Specific examples of the glycidyl
ether compound include phenyl glycidyl ether, o-phenyl glycidyl
ether, 1,4-bis(.beta.,.gamma.-epoxypropoxy)butane,
1,6-bis(.beta.,.gamma.-epoxypropoxy)hexane,
1,4-bis(.beta.,.gamma.-epoxypropoxy)benzene,
1-(.beta.,.gamma.-epoxypropoxy)-2-ethoxyethane,
1-(.beta.,.gamma.-epoxypropoxy)-2-benzyl oxyethane,
2,2-bis[p-(.beta.,.gamma.-epoxypropoxy)phenyl] propane, and
diglycidyl polyethers obtainable by reaction of bisphenols such as
2,2-bis(4-hydroxyphenyl)propane or 2,2-bis(4-hydroxyphenyl)methane
and epichlorohydrin, and these can be used alone, or can be used in
combination of two kinds of them or more. Further, a polyfunctional
epoxy-based compound having an epoxy group in the main chain or
side chain of a polymer is also suitably used, and examples thereof
include "EPOFRIEND" AT501 produced by Daicel Chemical Industries,
Ltd., "MODIPER" A4400 produced by Nippon Oils and Fats Co., Ltd.,
and "Joncryl" FA produced by BASF Corp.
[0049] Further, as the oxazoline-based compound having an oxazoline
group, a bisoxazoline compound is preferable, and specific examples
thereof include 2,2'-bis(2-oxazoline),
2,2'-bis(4-methyl-2-oxazoline), 2,2'-bis(4,4-dimethyl-2-oxazoline),
2,2'-bis(4-ethyl-2-oxazoline), 2,2'-bis(4,4'-diethyl-2-oxazoline),
2,2'-bis(4-propyl-2-oxazoline), 2,2'-bis(4-butyl-2-oxazoline),
2,2'-bis(4-hexyl-2-oxazoline), 2,2'-bis(4-phenyl-2-oxazoline),
2,2'-bis(4-cyclohexyl-2-oxazoline), 2,2'-bis(4-benzyl-2-oxazoline),
2,2'-p-phenylenebis(2-oxazoline), 2,2'-m-phenylenebis(2-oxazoline),
2,2'-o-phenylenebis(2-oxazoline),
2,2'-p-phenylenbbis(4-methyl-2-oxazoline),
2,2'-p-phenylenbbis(4,4-dimethyl-2-oxazoline),
2,2'-m-phenylenebis(4-methyl-2-oxazoline),
2,2'-m-phenylenebis(4,4-dimethyl-2-oxazoline),
2,2'-ethylenebis(2-oxazoline), 2,2'-tetramethylenebis(2-oxazoline),
2,2'-hexamethylenebis(2-oxazoline),
2,2'-octamethylenebis(2-oxazoline),
2,2'-decamethylenebis(2-oxazoline),
2,2'-ethylenebis(4-methyl-2-oxazoline),
2,2'-tetramethylenebis(4,4-dimethyl-2-oxazoline),
2,2'-9,9'-diphenoxyethanebis(2-oxazoline),
2,2'-cyclohexylenebis(2-oxazoline), and
2,2'-diphenylenebis(2-oxazoline). Among these,
2,2'-bis(2-oxazoline) is most preferable from the viewpoint of the
reactivity with polyester. Further, examples of a polyfunctional
oxazoline-based compound include a compound having a plurality of
oxazoline substituents in the side chain of a polymer, and examples
thereof include "Epocros" RPS-1005 produced by Nippon Shokubai Co.,
Ltd. Moreover, the bisoxazoline-based compound described above may
be used singly, or may be used in combination of two or more
species as long as it achieves our objectives.
[0050] These compounds are preferably low in volatility. Hence,
they are preferably high in a molecular weight. By using a high
molecular antihydrolysis segment, the volatility can be reduced.
Hence, the flame retardancy of the resulting polyester film can be
more enhanced. Further, the high molecular antihydrolysis segment
is preferable because it can reduce the crystallinity of a
polyester layer in which the crystalline polyester and the
inorganic particles are mixed and therefore it has the effect of
decreasing the curling of a film, for example, when this film has
an asymmetrical structure.
[0051] In the polyester film, as the antihydrolysis segment, a
compound having a carbodiimide group is preferable because it has a
large effect of disappearing the catalytic activity of a proton
originated from the carboxyl terminal group of the polyester.
Moreover, a polycarbodiimide-based compound with a high
polymerization degree is preferably used.
[0052] In the polyester film, the content Wb2 of the antihydrolysis
segment in the polyester layer P2 needs to be 0.02 to 1.5 mass % of
the layer P2. The content Wb2 of the antihydrolysis segment is more
preferably 0.05 to 1 mass %, and still more preferably 0.1 to 0.8
mass % of the layer P2. When the content Wb2 is less than 0.02 mass
%, the moisture-heat resistance of the layer P2 is significantly
deteriorated and therefore the moisture-heat resistance of the film
may be deteriorated. Further, it is not preferable because curling
may significantly increase when the polyester film has an
asymmetrical structure. Further, when the content Wb2 is more than
1.5 mass %, it is not preferable because the flame retardancy of
the polyester film may be significantly deteriorated. In the
polyester film, by setting the content Wb2 of the antihydrolysis
segment in the polyester layer P2 within the range of 0.01 to 1
mass % of the layer P2, it becomes possible to satisfactorily
combine the moisture-heat resistance and the flame retardancy.
Further, it becomes possible to satisfactorily combine the
moisture-heat resistance and the curling resistance even when the
polyester film has an asymmetrical structure.
[0053] In the polyester film, the polyester layer P1 preferably
further contains a antihydrolysis segment and the content Wb1 of
the antihydrolysis segment in the layer P1 is preferably 0.01 to 1
mass % of the layer P1. The content Wb1 of the antihydrolysis
segment is more preferably 0.02 to 0.8 mass %, and still more
preferably 0.05 to 0.5 mass % of the layer P1. When the content Wb1
is less than 0.01 mass %, the moisture-heat resistance of the
polyester film may be deteriorated. Further, when the content Wb1
is more than 1 mass %, the flame retardancy of the polyester film
may be deteriorated. In the polyester film, by setting the content
Wb1 of the antihydrolysis segment contained in the polyester layer
P1 within the range of 0.01 to 1 mass % of the layer P1, it becomes
possible to satisfactorily combine the moisture-heat resistance and
the flame retardancy. In addition, as the antihydrolysis segment,
the above-mentioned compounds can be suitably used.
[0054] In the polyester film, a ratio Wa2/Wb2 of the content Wa2 of
the inorganic particles in the polyester layer P2 to the content
Wb2 of the antihydrolysis segment in the polyester layer P2 is
preferably 10 to 500. The ratio Wa2/Wb2 is more preferably 3 to 50,
and still more preferably 10 to 30. When the ratio Wa2/Wb2 is less
than 1.5, the flame retardancy of the film may be deteriorated.
When the ratio Wa2/Wb2 is more than 100, the moisture-heat
resistance may be deteriorated. In the polyester film, when the
polyester layer P2 contains the antihydrolysis segment in such a
way that the ratio Wa2/Wb2 of the content Wa2 of the inorganic
particles to the content Wb2 of the antihydrolysis segment in the
layer P2 is 10 to 500, it is possible to satisfactorily combine the
moisture-heat resistance and the flame retardancy.
[0055] In the polyester film, a ratio Wa1/Wb1 of the content Wa1 of
the inorganic particles to the content Wb1 of the antihydrolysis
segment in the polyester layer P1 is preferably 1.5 to 100. The
ratio Wa1/Wb1 is more preferably 3 to 50, and still more preferably
10 to 30. When the ratio Wa1/Wb1 is less than 1.5, the flame
retardancy of the film may be deteriorated. When the ratio Wa1/Wb1
is more than 100, the moisture-heat resistance may be deteriorated.
In the polyester film, when the polyester layer P1 contains the
antihydrolysis segment such that the ratio Wa1/Wb1 of the content
Wa1 of the inorganic particles to the content Wb1 of the
antihydrolysis segment in the layer P1 is 1.5 to 100, it is
possible to satisfactorily combine the moisture-heat resistance and
the flame retardancy.
[0056] In the polyester film, the content Wb of the antihydrolysis
segment in the whole film is preferably 0.01 to 1.4 mass %. The
content Wb of the antihydrolysis segment is more preferably 0.02 to
1 mass %, 0.02 to 1, and still more preferably 0.05 to 0.5 mass %.
When Wb is less than 0.02, the moisture-heat resistance may be
deteriorated. Further, when Wb is more than 1.4 mass %, the flame
retardancy of the film may be deteriorated. In the polyester film,
by setting the content Wb of the antihydrolysis segment in the
whole film within the range of 0.02 to 1.4 mass %, it is possible
to satisfactorily combine the moisture-heat resistance and the
flame retardancy.
[0057] In the polyester film, a ratio Wa/Wb of the content Wa of
the inorganic particles in the whole film to the content Wb of the
antihydrolysis segment in the whole film is preferably 1 to 150.
The ratio Wa/Wb is more preferably 3 to 150, still more preferably
5 to 120, and particularly preferably 10 to 100. When the ratio
Wa/Wb is less than 1, the flame retardancy of the film may be
deteriorated. Further, when the ratio Wa/Wb is more than 150, the
moisture-heat resistance may be deteriorated. In the polyester
film, when the whole film contains the antihydrolysis segment in
such a way that the ratio Wa/Wb of the content Wa of the inorganic
particles to the content Wb of the antihydrolysis segment in the
whole film is 1 to 150, it is possible to satisfactorily combine
the moisture-heat resistance and the flame retardancy.
[0058] Further, to the polyester layer P1 and the polyester layer
P2 of the polyester film, other additives (e.g., a heat stabilizer,
an ultraviolet absorber, a weather stabilizer, an organic
lubricant, a pigment, a dye, a filler, an antistatic agent, and a
nucleating agent, however, the inorganic particles used herein are
not included) may be blended to such an extent that the positive
effect is not impaired. For example, when the ultraviolet absorber
is selected as the additive, the ultraviolet light resistance of
the polyester film can be enhanced. Examples of an organic
ultraviolet absorber compatible with a polyester include
ultraviolet absorbers such as salicylate-based, benzophenone-based,
benzotriazole-based, triazine-based, cyano acrylate-based
ultraviolet absorbers, and hindered amine-based ultraviolet
absorbers. Specific examples of the ultraviolet absorber include
salicylate-based ultraviolet absorbers such as p-t-butylphenyl
salicylate, and p-octylphenyl salicylate; benzophenone-based
ultraviolet absorbers such as 2,4-dihydroxybenzophenone,
2-hydroxy-4-methoxybenzophenone,
2-hydroxy-4-methoxy-5-sulfobenzophenone,
2,2',4,4'-tetrahydroxybenzophenone, and
bis(2-methoxy-4-hydroxy-5-benzoylphenyl)methane;
benzotriazole-based ultraviolet absorbers such as
2-(2'-hydroxy-5'-methylphenyl)benzotriazole,
2-(2'-hydroxy-5'-methylphenyl)benzotriazole, and 2,2'-methylenebis
[4-(1,1,3,3-tetramethylbutyl)-6-(2H benzotriazole-2-yl)phenol];
triazine-based ultraviolet absorbers such as
2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5[(hexyl)oxy]-phenol; cyano
acrylate-based ultraviolet absorbers such as
ethyl-2-cyano-3,3'-diphenyl acrylate; other ultraviolet absorbers
such as 2-(4,6-diphenyl-1,3,5-triazine-2-yl)-5-[(hexyl)oxy]-phenol;
hindered amine-based ultraviolet absorbers such as
bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, dimethyl
succinate-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethyl
piperidine polycondensate; other ultraviolet absorbers such as
nickel bis(octylphenyl)sulfide, and
2,4-di-t-butylphenyl-3',5'-di-t-butyl-4'-hydroxybenzoate.
[0059] The content of the organic ultraviolet absorber compatible
with a crystalline polyester is preferably 0.1 to 10 mass %, more
preferably 0.25 to 8 mass %, and still more preferably 0.5 to 5
mass % of the crystalline polyester. When the content of the
organic ultraviolet absorber compatible with a polyester is less
than 0.5 mass %, the ultraviolet light resistance is insufficient,
and the crystalline polyester may be degraded and mechanical
strength may be deteriorated when used for a long period. When the
content of the organic ultraviolet absorber is more than 10% by
weight, coloring of the crystalline polyester may increase.
[0060] The polyester film is composed of a laminate structure
comprising the polyester layer P1 and the polyester layer P2, which
respectively satisfy the above-mentioned requirements, and a
structure, in which the polyester layer P1 is an inner layer and
the polyester layer P2 is disposed on one side or both sides of the
layer P1, is preferred. Among others, the structure, in which one
outermost layer of the film is a layer P1 and the other outermost
layer is a layer P2, is preferable. The reason for this is that by
employing such a structure, it is possible to impart the
moisture-heat resistance, the flame retardancy and the
characteristic-improving effect based on containing the particles
to the film at an extremely high level, and it is possible to make
the high film adhesion (at the time of being bonded to other
member).
[0061] A total thickness of the polyester film is preferably 10 to
300 .mu.m, more preferably 20 to 200 .mu.m, and most preferably 30
to 150 .mu.m. When the thickness of the laminate is less than 10
.mu.m, the flatness of the film may be deteriorated. When the
thickness of the laminate is more than 300 .mu.m, a total thickness
of a solar-cell may become too large when the laminate is used as a
solar-cell back sheet.
[0062] In the polyester film, when the layer thickness of the
polyester layer P1 is denoted by T1 (.mu.m) and the layer thickness
of the polyester layer P2 is denoted by T2 (.mu.m), a ratio T1/T2
between both thicknesses is preferably 2 to 15. The ratio T1/T2 is
more preferably 4 to 10. When the ratio P1/P2 between the thickness
T1 of the layer P1 and the thickness T2 of the layer P2 is less
than 2, the moisture-heat resistance of the polyester film may be
deteriorated. Further, curling may increase too much when the
polyester film has an asymmetrical structure. Further, when the
ratio T1/T2 is more than 15, the effect of improving the
characteristics based on containing the inorganic particles tends
to be deteriorated. In the polyester film, by setting the ratio
T1/T2 within the range of 2 to 15, it is possible to exhibit the
maximum effect based on containing the inorganic particles without
deteriorating the moisture-heat resistance. Moreover, in the case
where the polyester film has an asymmetrical structure, the film
can be excellent in curling resistance.
[0063] The content Wa1 of the particles in the polyester film as a
whole is preferably 1 mass % or more. The content Wa1 is more
preferably 2.1 mass % or more, and still more preferably 5 mass %
or more. By setting the content Wa1 within this range, it becomes
possible to enhance the light-reflecting properties of the film,
for example, when titanium oxide or barium sulfate is used as
inorganic particles.
[0064] In the polyester film, the layer thickness T2 of the
polyester layer P2 is preferably 3.5 to 15 .mu.m. The layer
thickness T2 is more preferably 5 to 12 .mu.m, and still more
preferably 6 to 10 .mu.m. When the layer thickness T2 of the
polyester layer P2 is less than 3.5 .mu.m, the effect of improving
the characteristics based on the addition of the inorganic
particles tends to be deteriorated. Further, when T2 is more than
15 .mu.m, the moisture-heat resistance may be deteriorated.
Further, curling may increase too much when this film has an
asymmetrical structure. In the polyester film, by setting the layer
thickness T2 of the polyester layer P2 within the range of 3.5 to
15 .mu.m, it is possible to exhibit the effect based on the
addition of the particles without deteriorating the moisture-heat
resistance. Moreover, in the case where the polyester film has an
asymmetrical structure, the film can be excellent in curling
resistance.
[0065] The polyester film is preferably biaxially oriented. Since
an oriented crystallized portion can be formed effectively by
biaxial orientation, the moisture-heat resistance can be further
enhanced.
[0066] In the polyester film, it is preferred that the elongation
retention measured after treating for 48 hours in an atmosphere of
125.degree. C. and a humidity of 100% RH is 50% or more. The
elongation retention is more preferably 60% or more, still more
preferably 70% or more, and particularly preferably 80% or
more.
[0067] The elongation retention referred to herein is a value
measured based on ASTM-D882-97 (see 1999 version; ANNUAL BOOK OF
ASTM STANDARDS), and it can be determined from the following
formula (1) when the elongation at break of the untreated film is
taken as E0 and the elongation at break of the treated film is
taken as E.
Elongation retention (%)=E/E0.times.100 (1)
[0068] In addition, upon measurement, after the sample is cut out
into a shape of a test piece, the sample is treated, and the
treated sample is measured. By setting the elongation retention
within such a range, the moisture-heat resistance of the film
becomes even better, and this enables to make the moisture-heat
resistance of the back sheet using the polyester film better.
[0069] Further, in the polyester film, it is preferred that the
elongation retention, which is measured after irradiating for 48
hours by a metal halide lamp with an intensity of 100 mW/cm.sup.2
(wavelength range: 295 to 450 nm, peak wavelength: 365 nm) in an
atmosphere of 60.degree. C. and a humidity of 50% RH, is 20% or
more. The elongation retention is more preferably 25% or more,
still more preferably 30% or more, and particularly preferably 40%
or more. In addition, when the polyester film is irradiated by a
metal halide lamp, the polyester layer (layer P2) side of the
polyester film is exposed to light. Further, upon measurement,
after the sample is cut out into a shape of a test piece, the
sample is treated, and the treated sample is measured. By setting
the elongation retention within such a range, the ultraviolet light
resistance of the film can be better.
[0070] In the polyester film, it is preferred that the elongation
retention measured after treating for 48 hours in an atmosphere of
125.degree. C. and a humidity of 100% RH is 50% or more, and the
elongation retention, which is measured after irradiating for 48
hours by a metal halide lamp with an intensity of 100 mW/cm.sup.2
(wavelength range: 295 to 450 nm, peak wavelength: 365 nm) in an
atmosphere of 60.degree. C. and a humidity of 50% RH, is 20% or
more. Since the film, which satisfies these ranges simultaneously,
can be superior in moisture-heat resistance and ultraviolet light
resistance, it can maintain mechanical strength over a long period
in being used as a solar-cell back sheet, for example.
[0071] In the polyester film, it is preferred that curling of the
film, which is heat-treated at 140.degree. C. for 10 minutes, is 20
mm or less. The curling of the film is more preferably 15 mm or
less, still more preferably 10 mm or less, and particularly
preferably 5 mm or less, and the lower limit is 0 mm. When the
curling of the film is more than 20 mm, processing may become
difficult, for example, the film tends to contain air bubbles or
the film causes position gap when the film is subjected to
processing of combining with other materials (for example, bonding,
coating, etc.). Further, even when the film can be processed, the
resulting composite may cause curling, or curling may occur or
peeling may occur during the film is used. By keeping the curling
of the polyester film at 20 mm or less, the ability of the film to
be processed to combine the polyester film with other materials
(for example, bonding, coating, etc.) becomes better and the
resulting composite can be provided with curling resistance and
adhesion.
[0072] Moreover, the polyester film can form a laminate with other
films. Examples of other films include a polyester layer for
enhancing mechanical strength, an antistatic layer, a layer close
contact with other material, an ultraviolet light resistant layer
for increasing ultraviolet light resistance, a flame retardant
layer for providing flame retardancy, and a hard coat layer for
increasing impact resistance and abrasion resistance, and these
layers may be optionally selected depending on use. Specific
examples of other film at the time when the polyester film is used
as a film for a solar-cell back sheet, include a good adhesive
layer for improving the adhesion to another sheet material or a
sealing material (e.g., ethylene vinyl acetate) in which a power
generation element is embedded, an ultraviolet light resistant
layer, a flame retardant layer, and a conductive layer for
improving a voltage at which a partial discharge phenomenon being
measure of an insulation property occurs.
[0073] In the polyester film, examples of the method of forming a
laminate with other films include a method in which when each of
layers to be laminated is predominantly composed of a thermoplastic
resin, two different materials are charged into two separate
extruder, respectively, and melted materials are co-extruded from a
die onto a cooled casting drum to be formed into a sheet
(co-extrusion method), and a method in which a coating material is
charged into an extruder to be melt-extruded, and the melted
material is laminated on a sheet formed from a monofilm while
extruding the melted material from a die (melt lamination method),
a method in which films are separately prepared, and these films
are thermocompression bonded by a set of heated rolls (thermal
lamination method), a method of bonding the films to each other
through an adhesive (adhesion method), and a method of applying and
drying a coating solution formed by dissolving the material in a
solvent (coating method), and a mixed method thereof.
[0074] Next, an example of a method for producing the polyester
film will be described. As a method for obtaining the crystalline
polyester, a common polymerization method can be employed. For
example, a dicarboxylic acid component such as terephthalic acid or
a derivative thereof and a diol component such as ethylene glycol
are subjected to an ester exchange reaction by a well-known method.
Here, it is more preferable to use a component obtained by
esterifying a carboxyl group for the dicarboxylic acid component or
other copolymer component having a carboxylic acid group since the
number of the terminal groups of the carboxyl group can be reduced
and the moisture-heat resistance can be more enhanced.
[0075] Examples of a reaction catalyst include alkali metal
compounds, alkaline earth metal compounds, zinc compounds, lead
compounds, manganese compounds, cobalt compounds, aluminium
compounds, antimony compounds, and titanium compounds which are
conventionally known. It is preferable that an antimony compound or
a germanium compound, a titanium compound and a buffer agent are
added as polymerization catalysts at any stage prior to the
completion of polycondensation of the polyester. For such a method,
in the case of adding, for example, a germanium compound, it is
preferable to add germanium compound powders as they are. When an
antimony compound and/or a germanium compound are/is as the
polymerization catalyst, it is preferable from the viewpoint of
polycondensation reactivity or solid phase polymerization
reactivity that the concentration thereof is 50 to 300 ppm as an
antimony element or germanium element, and further it is preferable
from the viewpoint of heat resistance or moisture-heat resistance
that the concentration is 50 to 200 ppm. When the concentration is
more than 300 ppm, the polycondensation reactivity and the solid
phase polymerization reactivity are increased, but the carboxyl
terminal group may increase since a decomposition reaction in
re-melting is also accelerated, this may causes deterioration of
the heat resistance or the moisture-heat resistance. Examples of
antimony compounds and germanium compounds preferably used include
antimony pentoxide, antimony trioxide, and germanium dioxide, and
these can be selectively used depending on the object. For example,
a polymerization catalyst by which the color tone is best is the
germanium compound, a polymerization catalyst by which the solid
phase polymerization reactivity is better is the antimony compound,
and when the polyester film is produced by use of non-antimony
catalyst in consideration of environment, the titanium catalyst is
preferable because reactivity of a polycondensation reaction or
solid phase polymerization is high.
[0076] When a titanium compound is used as the polycondensation
catalyst, it is preferable from the viewpoint of polycondensation
reactivity or solid phase polymerization reactivity that the
concentration thereof is 0.1 to 20 ppm as a titanium element. When
the concentration is more than 20 ppm, the polycondensation
reactivity and the solid phase polymerization reactivity are
increased, but this may cause deterioration of the heat resistance,
the moisture-heat resistance, or color tone. Examples of the
titanium catalysts used as the polycondensation catalyst include
alkoxides such as tetrabutoxy titanate and tetraisopropyl titanate,
and titanium chelate compounds between titanium and lactic acid or
citric acid, and it is preferable from the viewpoint of heat
resistance, moisture-heat resistance and color tone that the
polycondensation catalyst is particularly the titanium chelate
compound.
[0077] Further, as a technique of reducing the number of the
carboxyl terminal groups of the polyester obtained by
polymerization, a trace of alkali metal compound such as potassium
hydroxide can be added during the time between the initial stage
and an intermediate stage of the esterification reaction, or
between before the start and the initial stage of the ester
exchange reaction, or a trace of magnesium compound, for example,
magnesium acetate, can be added between the completion of the
esterification reaction and the initial stage of the
polycondensation reaction, or before the start of the ester
exchange reaction to improve electrostatic charging properties.
[0078] Further, to reduce the number of the carboxyl terminal
groups of the polyester obtained by polycondensation in the range
of 20 equivalents/t or less and to increase the inherent viscosity
of the polyester, it is preferable that after the above
polymerization is performed, the polyester is heated at a
temperature of 190.degree. C. or higher and less than a melting
point of the polyester in a reduced pressure or in a stream of an
inert gas such as a nitrogen gas, that is, solid phase
polymerization is performed. In this case, it is preferable that as
a first step, a polyester with an inherent viscosity of 0.5 to 0.6
is polymerized by the above-mentioned method, and then as a second
step, the polyester is heated at a temperature of 190.degree. C. or
higher and less than a melting point of the polyester in a reduced
pressure or in a stream of an inert gas such as a nitrogen gas to
perform solid phase polymerization. When the inherent viscosity of
the polyester is 0.5 or less, the chip is easily split and its
configuration is irregular, and therefore irregular polymerization
may occur in the solid phase polymerization. When the inherent
viscosity of the polyester is more than 0.9, it is not preferable
because thermal degradation at the first step is severe, and
therefore the number of the carboxyl terminal groups of the
resulting polyester increases, and hydrolysis resistance may be
deteriorated in forming a film. In polymerization of a polyester
used in the polyester film, by adjusting the inherent viscosity at
the first step within the range of 0.5 to 0.6, the inherent
viscosity can be uniformly increased in a state in which the number
of the carboxyl terminal groups is kept low in performing the solid
phase polymerization. As a result of this, the hydrolysis
resistance can be more enhanced in forming a film.
[0079] Further, a method of adding the inorganic particles to the
polyester composing the layer P1 and/or the layer P2 is preferably
a method in which the crystalline polyester and the inorganic
particles are previously melt-kneaded by use of a vent type twin
screw kneading extruder or a tandem type extruder to form a high
level of master pellet and the master pellet is added as the
inorganic particles.
[0080] Further, when the polyester composing the layer P1 and/or
the layer P2 contains the antihydrolysis segment, any of a method
of mixing the polyester and the antihydrolysis segment at the time
of forming a film, and a method, in which a master pellet of a
polyester containing a high level of the antihydrolysis segment is
prepared in advance and the master pellet is diluted with a
polyester, is preferably employed. Preferable examples of preparing
a high level of master pellet include a method in which the
antihydrolysis segment is mixed with the polyester pellet and the
resulting mixture is melt-kneaded using a vent type twin screw
kneading extruder heated to temperatures of 265.degree. C. to
275.degree. C., preferably 270.degree. C. to 275.degree. C. to form
a high level of master. The inherent viscosity of the polyester
used at this time is preferably 0.7 to 1.6. The inherent viscosity
is more preferably 0.75 to 1.4. The inherent viscosity IV is still
more preferably 0.8 to 1.3. When the IV is less than 0.7, since the
amount of the carboxyl terminal of the polyester to be kneaded with
the antihydrolysis segment increases, a reaction with the
antihydrolysis segment takes place too much at the time of forming
a master. Therefore, the reaction between the antihydrolysis
segment and the polyester, which is a diluent of the antihydrolysis
segment, hardly occurs in extruding a raw material when a film is
formed, and hence the amount of the carboxyl terminal in the layer
P1 and/or the layer P2 cannot be reduced and the moisture-heat
resistance may be deteriorated. When the IV is larger than 1.6,
since the melt viscosity is too high, extrusion is unstable and
therefore preparation of the master pellet becomes difficult, and
if a temperature of the extruder is elevated to lower the melt
viscosity, the antihydrolysis segment is thermally decomposed, and
hence the amount of the carboxyl terminal in the layer P1 and/or
the layer P2 cannot be reduced and the moisture-heat resistance may
be deteriorated.
[0081] Next, a method for forming a film by using the
above-mentioned materials will be described.
[0082] First, a composition for the polyester layer P1 and a
composition for the polyester layer P2, which are respectively
prepared by mixing a polyester material, a master material
containing inorganic particles and a master material containing a
antihydrolysis segment, are respectively dried and then supplied,
in a nitrogen flow or in a reduced pressure, to two or more
extruders heated to temperatures of 265 to 280.degree. C., more
preferably 270 to 275.degree. C., and melted. Then, a polyester
layer (layer P1) and a polyester layer (layer P2) are combined into
one and laminated by use of a multimanifold die, a field block, a
static mixer, a pinole and the like, and a laminated layer is
co-extruded from a die to a cooled casting drum to form an
unstretched film. In this case, it is preferable that the film is
brought into close contact with a cooling body such as a casting
drum by an electrostatic force by using an electrode with shapes
such as a wire-shape, a tape-shape, a needle-shape, or a
knife-shape, and quenched and solidified.
[0083] The unstretched film thus formed is preferably biaxially
stretched at a temperature higher than a glass transition
temperature Tg of the polyester. The biaxial stretching, as
described above, may be sequential biaxial stretching in which
stretching in a longitudinal direction and stretching in a width
direction are separately performed, or simultaneous biaxial
stretching in which stretching in a longitudinal direction and
stretching in a width direction are simultaneously performed.
[0084] In the sequential biaxial stretching, the film was guided to
a set of rolls heated to a temperature of Tg (.degree. C.) of the
polyester or higher, Tg plus 5.degree. C. or higher and Tg plus
15.degree. C. or lower (more preferably, Tg plus 10.degree. C. or
lower), and stretched to a length 3 to 5 times longer in a
longitudinal direction (vertical direction, or machine direction),
and cooled by a set of rolls of 20 to 50.degree. C. It is preferred
that subsequently, the obtained film is guided to a tenter while
both ends of the film are grasped by clips, and stretched to a
length 3 to 5 times longer in a direction (width direction)
perpendicular to a longitudinal direction in an atmosphere heated
to a temperature of Tg plus 5.degree. C. or higher and Tg plus
30.degree. C. or lower (more preferably Tg plus 25.degree. C. or
lower, still more preferably Tg plus 20.degree. C. or lower).
[0085] While a stretching magnification is 3 to 5 times in each of
a longitudinal direction and a width direction for both of
simultaneous biaxial stretching and sequential biaxial stretching,
the polyester film is stretched in such a way that an area
magnification is 12 times or more, more preferably 13 times or
more, still more preferably 14 times or more, particularly
preferably 15 times or more, and most preferably 16 times or more.
Particularly when the area magnification is 13 times or more, it is
more preferable because the moisture-heat resistance of the
resulting film is more improved. When the area magnification is
less than 13 times, it is not preferable because the hydrolysis
resistance of the resulting biaxially stretched film may be
deteriorated. Further, when the area magnification is more than 20
times, breaking tends to occur in stretching the film.
[0086] Further, to complete the crystal orientation of the obtained
biaxially stretched film to impart a planar property and
dimensional stability, it is preferable that the film is heat
treated at a temperature less than a melting point of a crystalline
polyester for 1 to 30 seconds, and uniformly cooled gradually to
room temperature. Generally, when a heat treatment temperature is
low, heat shrinkage of a film becomes large, and therefore the heat
treatment temperature is preferably high to provide high thermal
dimensional stability.
[0087] However, when the heat treatment temperature is too high, it
is not preferable because an amorphous part is relaxed and
molecular movement becomes active, and therefore hydrolysis may
easily occur, or thermal crystallization after the hydrolysis may
be accelerated in an atmosphere of moisture-heat and embrittlement
may easily proceed. Accordingly, it is preferable to set the heat
treatment temperature in such a way that a value obtained by
subtracting the heat treatment temperature from a melting point of
the crystalline polyester is 40 to 90.degree. C., more preferably
50 to 80.degree. C., and still more preferably 55 to 75.degree.
C.
[0088] In heat treatment step, the film may be subjected to
relaxation treatment by 3 to 12% in a width direction or a
longitudinal direction as required. Subsequently, as required, the
film is subjected to corona discharge to enhance the adhesion to
other material and wound up, and thereby the polyester film can be
obtained.
[0089] Further, when another film is laminated on the polyester
film, in addition to the above-mentioned co-extrusion method, a
method in which another thermoplastic resin is melt-extruded, and
the melted resin is laminated on the prepared film while extruding
the melted resin from a die (melt lamination method), a method in
which the polyester film and a film made of another resin are
thermocompression bonded (thermal lamination method), a method in
which the polyester film and a film made of another resin are
bonded to each other through an adhesive (adhesion method), and a
method of applying another material onto the surface of the
polyester film to form a laminate (coating method), and a mixed
method thereof can be employed.
[0090] Since the polyester film has moisture-heat resistance and
can satisfactorily combine moisture-heat resistance and other
properties such as ultraviolet light resistance and
light-reflecting properties, it can be used for applications in
which long-term durability is valued, and is suitably used
particularly as a film for a solar-cell back sheet.
[0091] Further, to form a solar-cell back sheet by use of the
polyester film, for example, the polyester film, a sealing material
adhesion layer to improve the adhesion to a sealing material (e.g.,
ethylene-vinylene acetate copolymer (hereinafter, referred to as
EVA)), an anchor layer to increase the adhesion to the sealing
material adhesion layer, a moisture vapor barrier layer, an
ultraviolet absorbing layer to absorb ultraviolet light, a
light-reflecting layer to enhance power generation efficiency, a
light absorbing layer to develop design, and an adhesion layer to
bond each layer are configured, and particularly the polyester film
can be suitably used as an ultraviolet absorbing layer, a
light-reflecting layer and a light absorbing layer.
[0092] The polyester film in the case of using as an ultraviolet
absorbing layer in the solar-cell back sheet preferably has a
function of blocking light, a wavelength of which is shorter than
380 nm. Further, the polyester film in the case of being used as a
light-reflecting layer can prevent the degradation of a resin of an
inner layer by reflecting ultraviolet light, and can enhance power
generation efficiency by reflecting light, which has not been
absorbed by a solar-cell and reaches the back sheet, and backing it
to a cell. Further, the polyester film in the case of being used as
a light absorbing layer can prevent degradation of a resin of an
inner layer by absorbing ultraviolet light or can improve design of
the solar-cell.
[0093] The sealing material adhesion layer is a layer for improving
the adhesion to a sealing material such as an EVA-based resin which
seals a power generation element, and located at a position closest
to the power generation element, and contributes to the adhesion
between the back sheet and a system. Its material is not
particularly limited as long as it exhibits the adhesion to the
sealing material, and for example, mixtures of EVA,
EVA-ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl
acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA),
ethylene-methacrylic acid copolymer (EMMA), ionomer resin,
polyester, urethane resin, acrylic resin, polyethylene resin,
polypropylene resin and polyamide resin, are preferably used.
Further, the anchor layer is preferably formed for improving the
adhesion of the sealing material adhesion layer to the back sheet
as required. Its material is not particularly limited as long as
the adhesion to the sealing material adhesion layer is exhibited,
and for example, a mixture predominantly composed of an acrylic
resin and a polyester resin is preferably used.
[0094] A moisture vapor barrier layer is a layer which prevents the
moisture vapor from penetrating from a back sheet side in order to
prevent the degradation of a power generation element due to the
moisture vapor in composing a solar-cell. This layer is formed by
forming a layer of oxide such as silicon oxide or aluminum oxide or
a layer of metal such as aluminum on the surface of the film by a
well known method such as a vacuum deposition method or a
sputtering method. It is preferable that the thickness of the layer
is usually in the range of 100 to 200 .ANG.. In this case, there is
a method in which a gas barrier layer is formed directly on the
polyester film and a method in which a gas barrier layer is formed
on another film and this film is laminated on the surface of the
polyester film, and any of these methods is preferably employed.
Further, a method for laminating a metallic foil (for example,
aluminum foil) on the surface of the film can also be used. It is
preferable that the thickness of the metallic foil in such a case
is in the range of 10 to 50 .mu.m from the viewpoint of
processability and gas barrier properties.
[0095] By combining each of the above-mentioned layers with the
polyester film, the solar-cell back sheet is formed. In addition,
in the solar-cell back sheet, it is not necessary that all of the
above-mentioned layers have to be formed as an independent layer,
and it is a preferable aspect that these layer are formed as a
function-integrated layer which combines a plurality of functions.
Further, when the polyester film itself has already a required
function, other layers for providing various functions can be
omitted. For example, there may be cases where it is possible to
omit a light-reflecting layer when the polyester film has a
structure comprising a layer containing a white pigment and air
bubbles and has light-reflecting properties, to omit a light
absorbing layer when the polyester film has a structure comprising
a layer containing a light absorbing agent and has light absorbing
properties, and to omit an ultraviolet absorbing layer when the
polyester film has a structure comprising a layer containing an
ultraviolet absorber.
[0096] Since the polyester film is more superior moisture-heat
resistance than a conventional polyester film, a solar-cell back
sheet including the film can have higher moisture-heat resistance
and higher ultraviolet light resistance than a conventional back
sheet. To make the solar-cell back sheet exhibit the effect of high
moisture-heat resistance and high ultraviolet light resistance of
the polyester film, it is preferred that a volume ratio of the
polyester film to the whole back sheet is 5% or more. The volume
ratio is more preferably 10% or more, still more preferably 15% or
more, and particularly preferably 20% or more.
[0097] Further, in the solar-cell back sheet using the polyester
film, it is preferred that the polyester film is disposed at an
outermost position of the solar-cell back sheet.
[0098] The reason for this is that when a layer having excellent
moisture-heat resistance and flame retardancy is positioned at the
outermost layer, it is possible to suppress the occurrence of
cracks due to the surface degradation of the back sheet and hence
the moisture-heat resistance of the whole back sheet can be
enhanced, and the fire spread in a disaster such as a fire can be
suppressed.
[0099] Further, in the above aspect, it is preferred that at least
one outermost layer of the solar-cell back sheet is a layer P2.
Moreover, it is preferred that only one outermost layer of the back
sheet is a layer P2 of the polyester film. By employing such a
structure, it is possible to form a solar-cell back sheet in which
the effect based on the addition of the particles to the layer P2
is more exhibited.
[0100] Further, in the solar-cell back sheet using the polyester
film, it is preferred that the elongation retention measured after
leaving standing for 48 hours in an atmosphere of 125.degree. C.
and a humidity of 100% RH is 30% or more. The elongation retention
referred to herein is a value measured based on ASTM-D882-97 (see
1999 version; ANNUAL BOOK OF ASTM STANDARDS), and it can be
determined from the following formula (2) when the elongation at
break of the untreated solar-cell back sheet is taken as E0' and
the elongation at break of the treated solar-cell back sheet is
taken as E1'.
Elongation retention (%)=E1'/E0'.times.100 (2)
[0101] In addition, upon measurement, after the sample is cut out
into a shape of a test piece, the sample is treated, and the
treated sample is measured. The elongation retention is more
preferably 40% or more, still more preferably 50% or more, and
particularly preferably 60% or more. In the solar-cell back sheet,
when the elongation retention measured after leaving standing for
48 hours in an atmosphere of 125.degree. C. and a humidity of 100%
RH is less than 30%, it is not preferable because degradation due
to moisture-heat increases, for example, when a solar-cell equipped
with a back sheet is used for a long period, and the back sheet may
be fractured if some external impact is added to the solar-cell
(for example, a falling stone impinges on the solar-cell). The
polyester film is preferred because it can maintain the mechanical
strength of the solar-cell back sheet over a long period to form a
highly durable solar-cell by adjusting the elongation retention
measured after leaving standing for 48 hours in an atmosphere of
125.degree. C. and a humidity of 100% RH to 30% or more.
[0102] Further, in the solar-cell back sheet using the polyester
film, it is preferred that the elongation retention measured after
leaving standing for 72 hours in an atmosphere of 125.degree. C.
and a humidity of 100% RH is 10% or more. The elongation retention
is more preferably 20% or more, and still more preferably 30% or
more. The solar-cell back sheet is preferred because it can more
maintain the mechanical strength of the solar-cell back sheet over
a long period to form a more highly durable solar-cell by adjusting
the elongation retention within such a range.
[0103] Further, it is preferred that the elongation retention,
which is measured after irradiating for 48 hours by a metal halide
lamp with an intensity of 100 mW/cm.sup.2 (wavelength range: 295 to
450 nm, peak wavelength: 365 nm) in an atmosphere of 60.degree. C.
and a humidity of 50% RH, is 20% or more. In addition, when the
solar-cell back sheet using the polyester film is irradiated with
ultraviolet light, the polyester layer P2 side is a surface
irradiated with ultraviolet light. In addition, upon measurement,
after the sample is cut out into a shape of a test piece, the
sample is treated, and the treated sample is measured. The
elongation retention is more preferably 20% or more, still more
preferably 25% or more, particularly preferably 30% or more, and
most preferably 40% or more. In the polyester film, when the
elongation retention, which is measured after irradiating for 48
hours by a metal halide lamp with an intensity of 100 mW/cm.sup.2
(wavelength range: 295 to 450 nm, peak wavelength: 365 nm) in an
atmosphere of 60.degree. C. and a humidity of 50% RH, is less than
30%, it is not preferable because degradation due to ultraviolet
light increases, for example, when a solar-cell equipped with a
back sheet is used for a long period, and the back sheet may be
fractured if some external impact is added to the solar-cell (for
example, a falling stone impinges on the solar-cell). The
solar-cell back sheet is preferred because it can maintain the
mechanical strength of the solar-cell back sheet over a long period
to form a highly durable a solar-cell, when the elongation
retention, which is measured after irradiating for 48 hours by a
metal halide lamp with an intensity of 100 mW/cm.sup.2 (wavelength
range: 295 to 450 nm, peak wavelength: 365 nm) in an atmosphere of
60.degree. C. and a humidity of 50% RH, is adjusted to 20%.
[0104] In the solar-cell back sheet using the polyester film, it is
preferred that the elongation retention measured after leaving
standing for 48 hours in an atmosphere of 125.degree. C. and a
humidity of 100% RH is 30% or more, and the elongation retention,
which is measured after irradiating for 48 hours by a metal halide
lamp with an intensity of 100 mW/cm.sup.2 (wavelength range: 295 to
450 nm, peak wavelength: 365 nm) in an atmosphere of 60.degree. C.
and a humidity of 50% RH, is 20% or more. Moreover, it is preferred
that the elongation retention measured after leaving standing for
48 hours in an atmosphere of 125.degree. C. and a humidity of 100%
RH is 30% or more, the elongation retention measured after leaving
standing for 72 hours in an atmosphere of 125.degree. C. and a
humidity of 100% RH is 10% or more, and the elongation retention,
which is measured after irradiating for 48 hours by a metal halide
lamp with an intensity of 100 mW/cm.sup.2 (wavelength range: 295 to
450 nm, peak wavelength: 365 nm) in an atmosphere of 60.degree. C.
and a humidity of 50% RH, is 20% or more. The solar-cell back sheet
is preferred because by satisfying these requirements, it can
satisfactorily combine the moisture-heat resistance and the
ultraviolet light resistance and can maintain the mechanical
strength of the solar-cell back sheet over a long period to form a
more highly durable a solar-cell.
[0105] A thickness of the solar-cell back sheet is preferably 50 to
500 .mu.m, and more preferably 100 to 300 .mu.m. The thickness of
the solar-cell back sheet is still more preferably 125 to 200
.mu.m. When the thickness is less than 50 .mu.m, it becomes
difficult to secure the flatness of the back sheet. On the other
hand, when the thickness is more than 500 .mu.m, a thickness of the
whole solar-cell may become too large when the back sheet is
disposed in a solar-cell.
[0106] The solar-cell is characterized by using the solar-cell back
sheet using the polyester film. The solar-cell back sheet using the
polyester film enables enhancement of durability or to reduce its
thickness compared with conventional solar-cells making use of its
characteristics that the back sheet is superior in moisture-heat
resistance and other functions, in particular, ultraviolet light
resistance compared with conventional back sheets. An example of a
structure of the solar-cell back sheet is shown in FIG. 1. The
solar-cell is configured by bonding a transparent substrate 4 such
as glass, and a resin sheet, referred to as a solar-cell back sheet
1, to a power generation element, to which a lead (not shown in
FIG. 1) for extracting electricity is connected, and which is
sealed with a transparent sealing material 2 such as an EVA-based
resin, but the solar-cell is not limited to this configuration and
any configuration may be employed.
[0107] The power generation element 3 converts photo energy of
solar light to electric energy, and any element of crystal silicon,
polycrystal silicon, microcrystal silicon, amorphus silicon,
copper-indium-selenide, compound semiconductor, and dye sensitizer
can be used depending on an object, or in connection of a plural
cells in series or parallel depending on desired voltage or
current.
[0108] Since the transparent substrate 4 having a light
transmitting property is positioned at an outermost layer,
transparent materials having high transmittance, high weather
resistance, high antifouling property, and high mechanical strength
are used. In the solar-cell, the transparent substrate 4 having a
light transmitting property may be any one as long as it satisfies
the above-mentioned characteristics, and examples thereof include
glass, fluoro resins such as ethylene tetrafluoride-ethylene
copolymer (ETFE), polyvinyl fluoride resin (PVF), poly vinylidene
fluoride (PVDF), polytetrafluoroethylene (TFE),
tetrafluoroethylene-hexafluoropropylene copolymer (FEP),
polychlorotrifluoroethylene (CTFE), and poly vinylidene fluoride
resin; olefin-based resins; acrylic resins; and mixtures thereof.
When glass is used, reinforced one is more preferable. When a
transparent resin substrate is used, the above-mentioned resins
which are uniaxially or biaxially stretched are preferably used
from the viewpoint of mechanical strength.
[0109] Further, it is preferably performed that the surfaces of
these substrates are subjected to corona treatment, plasma
treatment, ozone treatment, or good adhesion treatment to provide
the adhesion to the EVA-based resins which are sealing materials of
the power generation element.
[0110] As the sealing material 2 for sealing the power generation
element, materials having high transparency, high weather
resistance, high adhesion, and high heat resistance are used to
cover and fix projections and depressions of the surface of the
power generation element with a resin, and protect the power
generation element from an external environment, and for the
purpose of electrical insulation, and to bond a substrate and a
back sheet having light transmitting property to the power
generation element. As the sealing materials, ethylene-vinylacetate
copolymer (EVA), ethylene-methylacrylate copolymer (EMA),
ethylene-ethylacrylate copolymer (EEA), ethylene-methacrylate
copolymer (EMAA), ionomer resin, polyvinyl butyral resin, and
mixtures thereof are preferably used. Among these resins,
ethylene-vinylacetate is more preferably used in that it has an
excellent balance among weather resistance, adhesion, filling
property, heat resistance, cold resistance, and impact
resistance.
[0111] As described above, when the solar-cell back sheet using the
polyester film is disposed in a solar-cell system, it is possible
to form a highly durable and/or a low profile solar-cell system
compared with a conventional solar-cell system. The solar-cell can
be suitably used for various applications, for example, solar light
power generation systems, power source of micro electronic parts
without being limited to outdoor use or indoor use.
Evaluation Method of Properties
[0112] A. Inherent Viscosity IV
[0113] A resin is dissolved in 100 ml of o-chlorophenol (solution
concentration C: 12 g/ml), the viscosity of the solution at
25.degree. C. was measure by use of an Ostwald viscometer. The
viscosity of a solvent is similarly measured. [.eta.] was
calculated from the following formula (3) by use of the obtained
solution viscosity, solvent viscosity, and this value was taken as
an inherent viscosity (IV).
.eta.sp/C=[.eta.]+K[.eta.].sup.2.times.C (3)
(in the above, .eta.sp=(solution viscosity)/(solvent viscosity)-1,
K is Huggins constant (0.343).)
[0114] B. Glass Transition Temperature Tg, Melting Point Tm,
Crystal Melting Heat Using a differential scanning calorimeter
"Robot DSC RDC220" manufactured by SEIKO Electronic and Disk
Session "SSC/5200" as a data analyzer, polyester resin samples were
measured by the following procedure according to JIS K 7122
(1987).
[0115] (1) 1st Run Measurement
[0116] Five mg of a resin sample was weighed in a sample pan and
heated at a temperature rising rate of 20.degree. C./min from
25.degree. C. to 300.degree. C. at a temperature rising rate of
20.degree. C./min, and maintained at the temperature for 5 minutes,
and then the temperature was quenched to 25.degree. C. or less.
[0117] (2) 2nd Run
[0118] Immediately after the completion of 1st Run measurement, the
resin sample was heated at a temperature rising rate of 20.degree.
C./min from room temperature to 300.degree. C. again.
[0119] In the obtained differential scanning calory measurement
chart of 2nd Run, a glass transition temperature of polyester Tg
was determined by applying a method described in "9.3 Method for
measuring glass transition point" in JIS K 7121 (1987) to a
step-like varying portion of glass transition (determined from an
intersection of a straight line which is equally distant in a
vertical axis direction from an extended line of a base line and a
curve of the step-like varying portion of glass transition). A
temperature of a peak top in the crystal melt peak was taken as a
melting point Tm of the polyester resin. Further, a crystal melting
heat was determined from a calory of a crystal melt peak based on
"9 Method for measuring transition heat" in JIS K 7121 (1987).
[0120] C. Content Wa1, Wa2 of Inorganic Particle
[0121] Each of the polyester layer P1 and the polyester layer P2
was shaved out from the film, and the contents Wa1, Wa2 of
inorganic particles of the shaved pieces were determined by the
following method.
[0122] A mass wa (g) of the shaved piece was measured. Then, the
piece was dissolved in o-chlorophenol, and a sedimentation
ingredient in an insoluble fraction was fractionated by centrifugal
separation. The obtained sedimentation ingredient was washed with
o-chlorophenol and centrifuged. In addition, a washing operation
was repeated until the centrifuged washing liquid did not become
whitish by addition of acetone. A mass wa' (g) of the obtained
sedimentation ingredient was measured and the content of the
inorganic particles was determined from the following formula
(4).
Content of inorganic particles (mass %)=wa'/wa.times.100 (4)
[0123] D. Content Wb1, Wb2 of Antihydrolysis Segment
[0124] Each of the polyester layer P1 and the polyester layer P2
was shaved out from the film, and the contents Wb1, Wb2 of the
antihydrolysis segment of the shaved pieces were determined by the
following method.
[0125] (i) Antihydrolysis Segment is Carbodiimide Compound
[0126] A structural identification of the antihydrolysis segment of
the shaved piece was performed by pyrolysis Gas
chromatography/pyrolysis Mass Spectrometry. Further, separately, a
nitrogen content (nig) contained per gram of the shaved piece was
determined by use of a trace nitrogen analyzer ND-100. Measurement
was carried out 5 times, and in quantitative determination, a
calibration curve prepared based on a pyridine standard solution
was used. The content of the antihydrolysis segment contained in
each layer was determined from a unit molecular weight and the
nitrogen content of the antihydrolysis segment.
[0127] (ii) Antihydrolysis Segment is Epoxy-Based Compound,
Oxazoline-Based Compound
[0128] The shaved piece was dissolved in a heavy solvent
(CDCl.sub.3/HFIP-d.sub.2 mixed solution). An insoluble fraction was
separated by centrifugal separation, and then by using the rest
solution, nuclear magnetic resonance (NMR) spectral analysis was
performed. The structures of the polyester and the antihydrolysis
segment were identified from the obtained results, and the content
of the antihydrolysis segment was determined from the peak
intensity ratio and the unit molecular weight. In addition, in the
structural identification, measurement was carried out in
combination with solvent extraction/separation as required.
[0129] E. Layer Thickness T1, T2, Layer Thickness Ratio T1/T2
[0130] Layer thicknesses T1, T2 and a lamination ratio T1/T2 are
determined by following the procedure described below. In addition,
measurement was carried out at 10 different points, and the average
value of 10 measurements was used for each of the thickness T1
(.mu.m) of the polyester layer P1, the thickness T2 (.mu.m) of the
polyester layer P2, and the layer thickness ratio T1/T2.
[0131] (A1) A film is cut in a direction perpendicular to a film
face without crushing a film cross-section in a thickness direction
using a microtome.
[0132] (A2) Then, the cut cross-section is observed using an
electron microscope and images of magnifications of 500 times are
obtained. In addition, an observation location is randomly
selected, but the images are taken in such a way that a vertical
direction of the image is parallel to a thickness direction of the
film and a horizontal direction of the image is parallel to a
planar direction of the film.
[0133] (A3) The thickness T1 of the polyester layer P1 and the
thickness T2 of the polyester layer P2 in the image obtained in the
above (A2) are determined.
[0134] (A4) The lamination ratio T1/T2 is determined by dividing T1
by T2.
[0135] F. Measurement of Elongation at Break
[0136] A sample was cut out into a size of 1 cm.times.20 cm based
on ASTM-D882-97 (see 1999 version; ANNUAL BOOK OF ASTM STANDARDS),
and the elongation retention at the time when the film was drawn
under the conditions of a chuck distance of 5 cm and a tensile
speed of 300 mm/min was measured. In addition, the number of
samples was 5, and the elongation at break in a longitudinal
direction and that in a width direction of the film were measured,
respectively, and an average of these measurements was
determined.
[0137] G. Elongation Retention after Moisture-Heat Resistance
Test
[0138] After the sample was cut out into a shape (1 cm.times.20 cm)
of a test piece, the test piece was treated for 48 hours under
conditions of 125.degree. C. and a humidity of 100% RH with a
pressure cooker manufactured by TABAI ESPEC Corp., and then the
elongation at break was measured according to the above-mentioned
paragraph F. In addition, the measurement was carried out 5 times,
and the elongation at break in a machine direction and that in a
transverse direction of the film were measured, respectively, and
an average of these measurements was taken as the elongation at
break E1. Further, the elongation at break E0 of an untreated film
was also measured according to the above-mentioned paragraph F, and
an elongation retention was calculated from the following formula
(1) using the resulting elongations at break E1, E2.
Elongation retention (%)=E1/E0.times.100 (1)
The obtained elongation retention was rated as follows. Elongation
retention is 80% or more: SS Elongation retention is 75% or more
and less than 80%: S Elongation retention is 70% or more and less
than 75%: A Elongation retention is 65% or more and less than 70%:
B Elongation retention is 60% or more and less than 65%: C
Elongation retention is 50% or more and less than 60%: D Elongation
retention is less than 50%: E
[0139] Symbols from SS to D indicate a good state, and among these,
SS is the most excellent.
[0140] With respect to the elongation at break of the back sheet,
as with Elongation Retention after Moisture-Heat Resistance Test,
the elongation at break of the untreated back sheet was taken as
E0', and the elongation at break E1' after treating for 48 hours
under conditions of 125.degree. C. and a humidity of 100% RH was
measured, and an elongation retention was calculated from the
following formula (2).
Elongation retention (%)=E1'/E0'.times.100 (2)
The obtained elongation retention was rated as follows. Elongation
retention is 60% or more: SS Elongation retention is 55% or more
and less than 60%: S Elongation retention is 50% or more and less
than 55%: A Elongation retention is 45% or more and less than 50%:
B Elongation retention is 40% or more and less than 45%: C
Elongation retention is 30% or more and less than 40%: D Elongation
retention is less than 30%: E
[0141] Symbols from SS to D indicate a good state, and among these,
SS is the most excellent.
[0142] H. Elongation Retention after Ultraviolet Light Resistance
Test
[0143] After the sample was cut out into a shape (1 cm.times.20 cm)
of a test piece, the test piece was irradiated for 48 hours under
conditions of 60.degree. C., a humidity of 60% RH and a illuminance
of 100 mW/cm.sup.2 (light source: metal halide lamp, wavelength
range: 295 to 450 nm, peak wavelength: 365 nm) using EYE Super UV
Tester SUV-W131 manufactured by IWASAKI ELECTRIC Co., Ltd., and
then the elongation at break was measured according to the
above-mentioned paragraph F. In addition, the measurement was
carried out 5 times, and the elongation at break in a machine
direction and that in a transverse direction of the film were
measured, respectively, and an average of these measurements was
taken as the elongation at break E2. Further, the elongation at
break E0 of an untreated film was also measured according to the
above-mentioned paragraph F, and an elongation retention was
calculated from the following formula (4) using the resulting
elongations at break E1, E2.
Elongation retention (%)=E2/E0.times.100 (4)
The obtained elongation retention was rated as follows. Elongation
retention is 40% or more: S Elongation retention is 35% or more and
less than 40%: A Elongation retention is 30% or more and less than
35%: B Elongation retention is 25% or more and less than 30%: C
Elongation retention is 20% or more and less than 25%: D Elongation
retention is less than 20%: E
[0144] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0145] With respect to the elongation at break of the back sheet,
as with Elongation Retention after Moisture-Heat Resistance Test,
the elongation at break of the untreated back sheet was taken as
E0', and the elongation at break E2' after irradiating for 48 hours
under conditions of 60.degree. C., a humidity of 60% RH and a
illuminance of 100 mW/cm.sup.2 (as UV light source, metal halide
lamp was used) was measured, and an elongation retention was
calculated from the following formula (5).
Elongation retention (%)=E2'/E0'.times.100 (5)
[0146] The obtained elongation retention was rated as follows.
Elongation retention is 40% or more: S Elongation retention is 35%
or more and less than 40%: A Elongation retention is 30% or more
and less than 35%: B Elongation retention is 25% or more and less
than 30%: C Elongation retention is 20% or more and less than 25%:
D Elongation retention is less than 20%: E
[0147] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0148] Here, the polyester layer P2 side of the polyester film was
irradiated with ultraviolet light.
[0149] I. Average Relative Reflectance
[0150] A spectral reflectance in a range of 400 to 700 nm was
measured at every wavelength of 10 nm using a spectrophotometer
U-3410 (manufactured by Hitachi, Ltd.), and an average of the
measured values was taken as an average relative reflectance. The
number of samples was 5, and the average relative reflectance of
each sample was measured, and an average thereof was calculated. An
integrating sphere of 60 mm in diameter (model No. 130-0632) was
used as a measurement unit and a spacer of the gradient angle of
10.degree. was attached. Further, as the standard white plate,
alumina oxide (model number: 210-0740) was used. Measurement was
carried out from the polyester layer P2 side.
The obtained reflection factor was rated as follows. Reflection
factor is 90% or more: S Reflection factor is 85% or more and less
than 90%: A Reflection factor is 80% or more and less than 85%: B
Reflection factor is 75% or more and less than 80%: C Reflection
factor is 60% or more and less than 75%: D Reflection factor is
less than 60%: E
[0151] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0152] J. Curling Resistance
[0153] A film was cut out into a size of 150 mm long.times.100 mm
wide, and left standing for 10 minutes in an atmosphere of no
breeze and 140.degree. C. using a vacuum drier (LKV-122)
manufactured by TABAI ESPEC Corp., and it was taken out and cooled.
Lifting heights of four corners of the cooled film were measured to
determine an average. In addition, measurement was carried out on
each of 5 samples which were cut out with a long side being
parallel to a longitudinal direction and 5 samples which were cut
out with a long side being parallel to a width direction and an
average of these measurements was calculated. Both sides of the
film were respectively brought into contact with a base to measure
a lifting height and a larger lifting height was taken as a curling
height.
The obtained curling height was rated as follows. Curling height is
2 mm or less: S Curling height is more than 2 mm and 5 mm or less:
A Curling height is more than 5 mm and 10 mm or less: B Curling
height is more than 10 mm and 15 mm or less: C Curling height is
more than 15 mm and 20 mm or less: D Curling height is more than 20
mm, or curling is large and therefore it is unmeasurable: E
[0154] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0155] K. Flame Retardancy
[0156] The flame retardancy was evaluated according to a UL94-VTM
testing method. A film test piece or back sheet test piece having a
size of 200 mm long.times.50 mm wide (marked line at a location 125
mm long) was wound cylindrically and attached vertically to a
clamp, and a piece of cotton was placed immediately beneath the
sample. A 20 mm long flame was brought into contact with the sample
for 3 seconds, and a burning time and the presence or absence of
ignition of cotton by a drip were observed. After extinguishing a
fire, the flame was brought into contact with the sample for 3
seconds again, and a subsequent burning time and a burning distance
were observed. This test was carried out on 10 samples. Each of the
resulting burned test pieces was observed and measured, and
flammability of a film was rated as follows.
Average burning distance is 95 mm or less: S Average burning
distance is more than 95 mm and 100 mm or less: A Average burning
distance is more than 100 mm and 105 mm or less: B Average burning
distance is more than 105 mm and 115 mm or less: C Average burning
distance is more than 115 mm and 125 mm or less: D Average burning
distance is more than 125 mm: E
[0157] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0158] Further, the flammability of a back sheet was rated as
follows.
Average burning distance is 75 mm or less: S Average burning
distance is more than 75 mm and 80 mm or less: A Average burning
distance is more than 80 mm and 85 mm or less: B Average burning
distance is more than 85 mm and 95 mm or less: C Average burning
distance is more than 95 mm and 110 mm or less: D Average burning
distance is more than 110 mm: E
[0159] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0160] L. Adhesion
[0161] A back sheet was cut out into a rectangle of 15 mm
wide.times.12 cm long, and a base material side of the back sheet
was bonded to an acrylic plate with a thickness of 2 mm having a
smooth surface with a double-faced tape, and an interface of the
polyester film of Examples or Comparative Examples was partially
peeled and a polyester film side of Examples or Comparative
Examples was hung on a load cell of a Tensilon tension tester (UTM
III manufactured by TOYO SOKKI Co., Ltd.). Next, the rest layer
side was gripped by a lower chuck and drawn at a peel speed of 300
mm/min in a direction of 90 degrees with respect to a planar
direction of the back sheet and peeling strength F (N/15 mm)
between the polyester film of the present invention and the rest
layer was measured. In addition, the peeling strength was
determined from an average of peeling forces T (N) in which a
peeling length was 50 mm or more excluding a rising part of an SS
curve.
The obtained peeling strength was rated as follows. Peeling
strength is 4 N/15 mm or more: S Peeling strength is 3.5 N/15 mm or
more and less than 4 N/15 mm: A Peeling strength is 3 N/15 mm or
more and less than 3.5 N/15 mm: B Peeling strength is 2.5 N/15 mm
or more and less than 3 N/15 mm: C Peeling strength is 2 N/15 mm or
more and less than 2.5 N/15 mm: D Peeling strength is less than 2
N/15 mm: E
[0162] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
[0163] M. Flatness
[0164] A film was cut out into a size of 150 mm long.times.100 mm
wide, and curling and deflection of the formed back sheet were
observed, and lifting heights of four corners of the back sheet
were measured to determine an average. In addition, measurement was
carried out on each of 5 samples which were cut out with a long
side being parallel to a longitudinal direction of the back sheet
and 5 samples which were cut out with a long side being parallel to
a width direction, and both sides of the back sheet were
respectively brought into contact with a base to measure a lifting
height to determine the respective averages, and a larger average
lifting height was taken as a curling height.
The obtained curling height was rated as follows. Curling height is
2 mm or less: S Curling height is more than 2 mm and 5 mm or less:
A Curling height is more than 5 mm and 8 mm or less: B Curling
height is more than 8 mm and 11 mm or less: C Curling height is
more than 11 mm and 15 mm or less: D Curling height is more than 15
mm, or curling is large and therefore it is unmeasurable: E
[0165] Symbols from S to D indicate a good state, and among these,
S is the most excellent.
EXAMPLES
[0166] Hereinafter, our films, back sheets and solar cells will be
described by way of examples, but this disclosure is not limited to
these examples.
(Raw Material)
[0167] Polyester:
[0168] PET: Dimethyl terephthalate was used as an acid component
and ethylene glycol was used as a diol component, and germanium
oxide (polymerization catalyst) was added so as to be 300 ppm on
the germanium atom equivalent basis with respect to the resulting
polyester pellet, and the polycondensation reaction of the
resulting mixture was performed to prepare a polyethylene
terephthalate pellet having an inherent viscosity of 0.54 and the
number of the carboxyl terminal groups of 13 equivalents/t. The
obtained polyethylene terephthalate was dried at 160.degree. C. for
6 hours and then crystallized. Thereafter, solid phase
polymerization was performed at 220.degree. C. for 8 hours in a
reduced pressure of 0.3 Torr to obtain polyethylene terephthalate
having an inherent viscosity of 0.80 and the number of the carboxyl
terminal groups of 12 equivalents/t. In addition, this resin had a
glass transition temperature Tg of 83.degree. C., a melting point
Tm of 255.degree. C., and crystal melting heat of 36 .mu.g.
[0169] Antihydrolysis Segment
[0170] Aromatic polycarbodiimide-based compound: "Stabaxol" P400
(produced by Rhein Chemie Rheinau GmbH) was used.
[0171] Epoxy-based compound: "EPOFRIEND" AT501 (produced by Daicel
Chemical Industries, Ltd., oxirane oxygen concentration 1.5 wt %)
was used.
[0172] Aliphatic polycarbodiimide-based compound: "CARBODILITE"
LA-1 (produced by Nisshinbo Holdings Inc.) was used.
[0173] Oxazoline-based compound: "Epocros" RPS-1005 (produced by
Nippon Shokubai Co., Ltd.) was used.
Reference Example 1
[0174] One hundred parts by weight of PET and 100 parts by weight
of rutile type titanium oxide particles having an average particle
diameter of 200 nm were melt-kneaded in a vented twin screw
kneading extruder maintained at 260.degree. C., melt-extruded and
discharged into a strand, and the discharged resin was cooled by
water of 25.degree. C. and immediately cut to prepare a master
batch of titanium oxide (MB-TiO2).
Reference Example 2
[0175] One hundred parts by weight of PET and 100 parts by weight
of barium sulfate having an average particle diameter of 700 nm
were melt-kneaded in a vented twin screw kneading extruder
maintained at 260.degree. C., melt-extruded and discharged into a
strand, and the discharged resin was cooled by water of 25.degree.
C. and immediately cut to prepare a master batch of barium sulfate
(MB-BaSO.sub.4).
Reference Example 3
[0176] Ninety parts by mass of the PET obtained in the
above-mentioned PET and 10 parts by mass of an aromatic
polycarbodiimide-based compound "Stabaxol" P400 (produced by Rhein
Chemie Rheinau GmbH) as an antihydrolysis segment were supplied to
a vent type twin screw kneading extruder (manufactured by Japan
Steel Works, Ltd., screw diameter 30 mm, screw length/screw
diameter 45.5) of a co-rotating type, in which a kneading section
with a kneading paddle heated to 265.degree. C. was disposed, and
the resulting mixture was melt-extruded at a screw rotational speed
of 200 rpm and discharged into a strand, and the discharged resin
was cooled by water of 25.degree. C. and immediately cut to prepare
a master batch of an antihydrolysis segment (MB-1).
Reference Example 4
[0177] Ninety parts by mass of the above-mentioned PET and 10 parts
by mass of an epoxy-based compound "EPOFRIEND" AT501 (produced by
Daicel Chemical Industries, Ltd., oxirane oxygen concentration 1.5
wt %) as an antihydrolysis segment were supplied to a vent type
twin screw kneading extruder (manufactured by Japan Steel Works,
Ltd., screw diameter 30 mm, screw length/screw diameter 45.5) of
co-rotating type, in which a kneading section with a kneading
paddle heated to 265.degree. C. was disposed, and the resulting
mixture was melt-extruded at a screw rotational speed of 200 rpm
and discharged into a strand, and the discharged resin was cooled
by water of 25.degree. C. and immediately cut to prepare a material
blend chip of an antihydrolysis segment (MB-2).
Reference Example 5
[0178] A raw material blend chip of an antihydrolysis segment
(MB-3) was prepared in the same manner as in Reference Example 2
except for using an aliphatic polycarbodiimide-based compound
"CARBODILITE" LA-1 (produced by Nisshinbo Holdings Inc.) as an
antihydrolysis segment.
Reference Example 6
[0179] A raw material blend chip of an antihydrolysis segment
(MB-4) was prepared in the same manner as in Reference Example 2
except for using an oxazoline-based compound "Epocros" RPS-1005
(produced by Nippon Shokubai Co., Ltd.) as an antihydrolysis
segment.
Example 1
[0180] Using a main extruder and a sub-extruder, to the main
extruder (uniaxial extruder), a mixture, which was prepared by
mixing PET, the titanium oxide raw material (MB-TiO2) obtained in
Reference Example 1 and the master batch of an antihydrolysis
segment (MB-1) obtained in Reference Example 3 in such a way that
the content of titanium oxide and the content of a antihydrolysis
segment were the composition shown in Table 1, was vacuum-dried at
180.degree. C. for 2 hours, and then supplied, and the resulting
mixture was melt-extruded at 275.degree. C., filtered with a 80
.mu.m cut filter, and guided to a T-diedie. On the other hand, to
the sub-extruder, a mixture, which was prepared by mixing PET, the
titanium oxide material (MB-TiO2) obtained in Reference Example 1
and the master batch of an antihydrolysis segment (MB-1) obtained
in Reference Example 3 such that the content of titanium oxide and
the content of an antihydrolysis segment were the composition shown
in Table 1, was vacuum-dried at 180.degree. C. for 2 hours, and
then supplied. Next, a polyester layer (layer P2) supplied from a
sub-extruder was joined to one side of a polyester layer (layer P1)
supplied from a main extruder such that the thickness proportion
between the layer P1 and the layer P2 was 6:1, and two melt layers
were coextruded into a laminate from a T-die die to form a
laminated sheet, and the laminated sheet was brought into close
contact with a drum, in which a surface temperature was maintained
at 20.degree. C., by an electrostatic charging method, cooled and
solidified to obtain an unoriented (unstretched) laminated
sheet.
[0181] Subsequently, the unstretched laminated sheet was preheated
by a set of rolls heated to 85.degree. C., and then stretched to a
length 3.5 times longer in a longitudinal direction (vertical
direction) by use of a heating roll of 90.degree. C., and cooled by
a set of rolls of 25.degree. C. to obtain a uniaxial stretched
film.
[0182] The obtained uniaxial stretched film was guided to a
preheating zone of 90.degree. C. in a tenter while both ends of the
film were grasped by clips. Subsequently, the film was stretched to
a length 4.1 times longer in a direction (width direction)
perpendicular to a longitudinal direction in a heating zone
maintained at 100.degree. C. Moreover, subsequently, the resulting
film was subjected to a heat treatment at 210.degree. C. for 20
seconds in a heat-treating zone in the tenter and subjected to
relaxation of 4% in a width direction at 150.degree. C. Then, the
film was uniformly slowly-cooled to obtain a polyester film having
a thickness of 50 .mu.m.
[0183] A layer thickness and a layer thickness ratio of the
obtained film were determined, and the results thereof are shown in
Table 2. Further, an average relative reflectance, mechanical
properties after the moisture-heat resistance test, mechanical
properties after the ultraviolet light resistance test, curling and
flame retardancy of the film were evaluated. As the results of
these, it was found that as shown in Table 2, this film had
excellent moisture-heat resistance, ultraviolet light resistance,
light-reflecting properties and flame retardancy.
[0184] Onto the surface of a layer P1 of the obtained film, an
adhesive (a mixture of 90 parts by mass of "TAKERAK" (trademark)
A-310 (produced by MITSUI TAKEDA CHEMICALS, INC.) and 10 parts by
weight of "TAKENATE" (trademark) A3 (produced by MITSUI TAKEDA
CHEMICALS, INC.)) was applied, and dried at 150.degree. C. for 30
seconds, and then on the face of this, a biaxially stretched
polyester film "Lumirror" (trademark) X10S (produced by Toray
Industries, Inc.) having a thickness of 75 .mu.m was overlaid, and
both films were bonded to each other through a laminator heated to
50.degree. C. Further, to the biaxially stretched polyester film
(X10S) side of the bonded film, a gas barrier film "Barrialox"
(trademark) VM-PET1031HGTS (produced by TORAY ADVANCED FILM Co.,
Ltd.) having a thickness of 12 .mu.m was bonded by use of the above
adhesive with a vapor deposition layer facing outward to prepare a
solar-cell back sheet having a thickness of 150 .mu.m. The
flatness, adhesion, moisture-heat resistance, flame retardancy,
ultraviolet light resistance, ultraviolet light resistance and
light-reflecting properties of the obtained back sheet were
evaluated, and consequently, it was found that as shown in Table 2,
the solar-cell back sheet had good flatness, adhesion,
moisture-heat resistance, flame retardancy, ultraviolet light
resistance and light-reflecting properties.
Examples 2 to 22, 24 to 30, 32 to 57, 59 to 65, 67 to 80
[0185] Polyester films were obtained in the same manner as in
Example 1 except for using values shown in Table 1 as the inorganic
particle contents Wa1 and Wa2, the antihydrolysis segment contents
Wb 1 and Wb2 and the layer thickness ratios of lamination
layers.
[0186] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling and flame retardancy of the films were
evaluated. As the results of these, it was found that as shown in
Table 2, these films had excellent moisture-heat resistance,
ultraviolet light resistance, light-reflecting properties and flame
retardancy.
[0187] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good flatness, adhesion, moisture-heat resistance,
flame retardancy, ultraviolet light resistance and light-reflecting
properties.
Examples 23, 31, 58 and 66
[0188] Polyester films were obtained in the same manner as in
Example 1 except for using values shown in Table 1 as the inorganic
particle contents Wa1 and Wa2, the antihydrolysis segment contents
Wb1 and Wb2 and the layer thickness ratios of lamination
layers.
[0189] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
films were evaluated. As the results of these, it was found that as
shown in Table 2, these films had excellent moisture-heat
resistance, ultraviolet light resistance, light-reflecting
properties and flame retardancy.
[0190] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good flatness, moisture-heat resistance, flame
retardancy, ultraviolet light resistance and light-reflecting
properties despite low adhesion.
Examples 81, 84 and 85
[0191] Polyester films were obtained in the same manner as in
Example 1 except for using respectively, as a master batch of the
antihydrolysis segment, MB-2 obtained in Reference Example 4 for
Example 81, MB-3 obtained in Reference Example 5 for Example 84,
and MB-4 obtained in Reference Example 6 for Example 85, to obtain
the composition shown in Table 1.
[0192] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
films were evaluated. As the results of these, it was found that as
shown in Table 2, these films had excellent moisture-heat
resistance, ultraviolet light resistance, light-reflecting
properties and flame retardancy.
[0193] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good flatness, adhesion, moisture-heat resistance,
flame retardancy, ultraviolet light resistance and light-reflecting
properties.
Example 82
[0194] A polyester film was obtained in the same manner as in
Example 1 except for using MB-BaSO4 obtained in Reference Example 2
as a master batch of the inorganic particle to obtain the
composition shown in Table 1.
[0195] A layer thickness and a layer thickness ratio of lamination
layers of the obtained film were determined, and the results
thereof are shown in Table 2. Further, an average relative
reflectance, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
film were evaluated. As the results of these, it was found that as
shown in Table 2, this film had excellent moisture-heat resistance,
ultraviolet light resistance, light-reflecting properties and flame
retardancy.
[0196] Further, a solar-cell back sheet was prepared in the same
manner as in Example 1 by use of the film, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheet were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheet had good flatness, adhesion, moisture-heat resistance,
flame retardancy, ultraviolet light resistance and light-reflecting
properties.
Example 83
[0197] A polyester film (laminated film of three layers) was
obtained in the same manner as in Example 1 except for joining two
polyester layers (layer P2) supplied from a sub-extruder to both
sides of a polyester layer (layer P1) supplied from a main
extruder, respectively, in such a way that the thickness proportion
among the layer P2, the layer P1 and the layer P2 was 1:12:1.
[0198] A layer thickness and a layer thickness ratio of lamination
layers of the obtained film were determined, and the results
thereof are shown in Table 2. Further, an average relative
reflectance, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
film were evaluated. As the results of these, it was found that as
shown in Table 2, this film had excellent moisture-heat resistance,
ultraviolet light resistance, light-reflecting properties and flame
retardancy.
[0199] Further, a solar-cell back sheet was prepared in the same
manner as in Example 1 except for applying the adhesive to the side
of the layer P2 by use of the film, and the flatness, adhesion,
moisture-heat resistance, flame retardancy, ultraviolet light
resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheet were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheet had good flatness, adhesion, moisture-heat resistance,
flame retardancy, ultraviolet light resistance and light-reflecting
properties despite low adhesion.
Comparative Examples 1, 5, 9, 13, 17 and 18
[0200] Polyester films were obtained in the same manner as in
Example 1 except for using values shown in Table 1 as the inorganic
particle contents Wa1 and Wa2, the antihydrolysis segment contents
Wb1 and Wb2 and the layer thickness ratios of lamination
layers.
[0201] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
films were evaluated. As the results of these, it was found that as
shown in Table 2, these films had excellent moisture-heat
resistance, light-reflecting properties and flame retardancy, but
they had low ultraviolet light resistance in comparison with
Examples.
[0202] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good flatness, adhesion, moisture-heat resistance,
flame retardancy and light-reflecting properties, but they had low
ultraviolet light resistance.
Comparative Examples 2, 4, 6 and 8
[0203] Polyester films were obtained in the same manner as in
Example 1 except for using values shown in Table 1 as the inorganic
particle contents Wa1 and Wa2, the antihydrolysis segment contents
Wb1 and Wb2 and the layer thickness ratios of lamination
layers.
[0204] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
films were evaluated. As the results of these, it was found that as
shown in Table 2, these films had excellent ultraviolet light
resistance, light-reflecting properties and flame retardancy, but
they had low flatness and low moisture-heat resistance in
comparison with Examples.
[0205] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good flatness, adhesion, flame retardancy,
ultraviolet light resistance and light-reflecting properties, but
they had low moisture-heat resistance.
Comparative Examples 3, 7, 11 and 15
[0206] Polyester films were obtained in the same manner as in
Example 1 except for using values shown in Table 1 as the inorganic
particle contents Wa1 and Wa2, the antihydrolysis segment contents
Wb1 and Wb2 and the layer thickness ratios of lamination
layers.
[0207] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling resistance and flame retardancy of the
films were evaluated. As the results of these, it was found that as
shown in Table 2, these films had excellent moisture-heat
resistance, ultraviolet light resistance, light-reflecting
properties and flame retardancy, but they had low curling
resistance in comparison with Examples.
[0208] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good adhesion, moisture-heat resistance,
ultraviolet light resistance, light-reflecting properties and flame
retardancy, but they had low flatness.
Comparative Examples 10, 12, 14 and 16
[0209] Polyester films were obtained in the same manner as in
Example 1 except for using values shown in Table 1 as the inorganic
particle contents Wa1 and Wa2, the antihydrolysis segment contents
Wb1 and Wb2 and the layer thickness ratios of lamination
layers.
[0210] Layer thicknesses and layer thickness ratios of lamination
layers of the obtained films were determined, and the results
thereof are shown in Table 2. Further, average relative
reflectances, mechanical properties after the moisture-heat
resistance test, mechanical properties after the ultraviolet light
resistance test, curling and flame retardancy of the films were
evaluated. As the results of these, it was found that as shown in
Table 2, these films had excellent moisture-heat resistance,
ultraviolet light resistance, light-reflecting properties and flame
retardancy, but they had low flame retardancy in comparison with
Examples.
[0211] Further, solar-cell back sheets were prepared in the same
manner as in Example 1 by use of these films, and the flatness,
adhesion, moisture-heat resistance, flame retardancy, ultraviolet
light resistance, ultraviolet light resistance and light-reflecting
properties of the prepared back sheets were evaluated, and
consequently, it was found that as shown in Table 2, the solar-cell
back sheets had good adhesion, moisture-heat resistance,
ultraviolet light resistance, light-reflecting properties and
flatness, but they had low flame retardancy.
TABLE-US-00001 TABLE 1-1 Composition Layer P1 Layer P2 layer P2
layer P1 layer Inorganic Inorganic Antihydrolysis Antihydrolysis
thickness particle particle agent agent of laminate Wa1 Wa2 Wb2 Wa2
- Wa1 Wb1 P1 P2 T1/T2 Wa (mass %) (mass %) (mass %) (mass %) (mass
%) (.mu.m) (.mu.m) (--) (mass %) Example 1 1 13 0.1 12 0.1 42.9 7.1
6.0 2.7 Example 2 0.8 13 0.1 12.2 0.1 42.9 7.1 6.0 2.5 Example 3
0.5 13 0.1 12.5 0.1 42.9 7.1 6.0 2.3 Example 4 0.1 13 0.1 12.9 0.1
42.9 7.1 6.0 1.9 Example 5 0 13 0.1 13 0.1 42.9 7.1 6.0 1.8 Example
6 1 10 0.1 9 0.1 42.9 7.1 6.0 2.3 Comparative Example 1 1 8 0.1 7
0.1 42.9 7.1 6.0 2.0 Example 7 1 13 0.08 12 0.1 42.9 7.1 6.0 2.7
Example 8 1 13 0.05 12 0.1 42.9 7.1 6.0 2.7 Example 9 1 13 0.02 12
0.1 42.9 7.1 6.0 2.7 Comparative Example 2 1 13 0.01 12 0.1 42.9
7.1 6.0 2.7 Example 10 1 20 0.1 19 0.1 42.9 7.1 6.0 3.7 Example 11
0.8 20 0.1 19.2 0.1 42.9 7.1 6.0 3.5 Example 12 0.5 20 0.1 19.5 0.1
42.9 7.1 6.0 3.3 Example 13 0.1 20 0.1 19.9 0.1 42.9 7.1 6.0 2.9
Example 14 0 20 0.1 20 0.1 42.9 7.1 6.0 2.8 Example 15 1 23 0.1 22
0.1 42.9 7.1 6.0 4.1 Example 16 1 25 0.1 24 0.1 42.9 7.1 6.0 4.4
Comparative Example 3 1 27 0.1 26 0.1 42.9 7.1 6.0 4.7 Example 17 1
20 0.08 19 0.1 42.9 7.1 6.0 3.7 Example 18 1 20 0.05 19 0.1 42.9
7.1 6.0 3.7 Example 19 1 20 0.02 19 0.1 42.9 7.1 6.0 3.7
Comparative Example 4 1 20 0.01 19 0.1 42.9 7.1 6.0 3.7 Example 20
3 13 0.1 10 0.1 42.9 7.1 6.0 4.4 Example 21 4 13 0.1 9 0.1 42.9 7.1
6.0 5.3 Example 22 5 13 0.1 8 0.1 42.9 7.1 6.0 6.1 Example 23 6 13
0.1 7 0.1 42.9 7.1 6.0 7.0 Example 24 3 10 0.1 7 0.1 42.9 7.1 6.0
4.0 Comparative Example 5 3 8 0.1 5 0.1 42.9 7.1 6.0 3.7 Example 25
3 13 0.08 10 0.1 42.9 7.1 6.0 4.4 Example 26 3 13 0.05 10 0.1 42.9
7.1 6.0 4.4 Example 27 3 13 0.02 10 0.1 42.9 7.1 6.0 4.4
Comparative Example 6 3 13 0.01 10 0.1 42.9 7.1 6.0 4.4 Example 28
3 22 0.1 19 0.1 42.9 7.1 6.0 5.7 Example 29 4 22 0.1 18 0.1 42.9
7.1 6.0 6.6 Example 30 5 22 0.1 17 0.1 42.9 7.1 6.0 7.4 Example 31
6 22 0.1 16 0.1 42.9 7.1 6.0 8.3 Example 32 3 25 0.1 22 0.1 42.9
7.1 6.0 6.1 Comparative Example 7 1 27 0.1 26 0.1 42.9 7.1 6.0 4.7
Example 33 3 22 0.08 19 0.1 42.9 7.1 6.0 5.7 Example 34 3 22 0.05
19 0.1 42.9 7.1 6.0 5.7 Example 35 3 22 0.02 19 0.1 42.9 7.1 6.0
5.7 Comparative Example 8 3 22 0.01 19 0.1 42.9 7.1 6.0 5.7 Example
36 1 13 0.8 12 0.1 42.9 7.1 6.0 2.7 Example 37 0.8 13 0.8 12.2 0.1
42.9 7.1 6.0 2.5 Example 38 0.5 13 0.8 12.5 0.1 42.9 7.1 6.0 2.3
Example 39 0.1 13 0.8 12.9 0.1 42.9 7.1 6.0 1.9 Example 40 0 13 0.8
13 0.1 42.9 7.1 6.0 1.8 Example 41 1 10 0.8 9 0.1 42.9 7.1 6.0 2.3
Comparative Example 9 1 8 0.8 7 0.1 42.9 7.1 6.0 2.0 Example 42 1
10 0.9 9 0.1 42.9 7.1 6.0 2.3 Example 43 1 10 1 9 0.1 42.9 7.1 6.0
2.3 Example 44 1 10 1.5 9 0.1 42.9 7.1 6.0 2.3 Comparative Example
10 1 10 1.6 9 0.1 42.9 7.1 6.0 2.3 Example 45 1 20 0.8 19 0.1 42.9
7.1 6.0 3.7 Example 46 0.8 20 0.8 19.2 0.1 42.9 7.1 6.0 3.5 Example
47 0.5 20 0.8 19.5 0.1 42.9 7.1 6.0 3.3 Example 48 0.1 20 0.8 19.9
0.1 42.9 7.1 6.0 2.9 Example 49 0 20 0.8 20 0.1 42.9 7.1 6.0 2.8
Example 50 1 23 0.8 22 0.1 42.9 7.1 6.0 4.1 Example 51 1 25 0.8 24
0.1 42.9 7.1 6.0 4.4 Comparative Example 11 1 27 0.8 26 0.1 42.9
7.1 6.0 4.7 Example 52 1 22 0.9 21 0.1 42.9 7.1 6.0 4.0 Example 53
1 22 1 21 0.1 42.9 7.1 6.0 4.0 Example 54 1 22 1.5 21 0.1 42.9 7.1
6.0 4.0 Comparative Example 12 1 22 1.6 21 0.1 42.9 7.1 6.0 4.0
Example 55 3 13 0.8 10 0.1 42.9 7.1 6.0 4.4 Example 56 4 13 0.8 9
0.1 42.9 7.1 6.0 5.3 Example 57 5 13 0.8 8 0.1 42.9 7.1 6.0 6.1
Example 58 6 13 0.8 7 0.1 42.9 7.1 6.0 7.0 Example 59 3 10 0.8 7
0.1 42.9 7.1 6.0 4.0 Comparative Example 13 3 8 0.8 5 0.1 42.9 7.1
6.0 3.7 Example 60 3 13 0.9 10 0.1 42.9 7.1 6.0 4.4 Example 61 3 13
1 10 0.1 42.9 7.1 6.0 4.4 Example 62 3 13 1.5 10 0.1 42.9 7.1 6.0
4.4 Comparative Example 14 3 13 1.6 10 0.1 42.9 7.1 6.0 4.4 Example
63 3 22 0.8 19 0.1 42.9 7.1 6.0 5.7 Example 64 4 22 0.8 18 0.1 42.9
7.1 6.0 6.6 Example 65 5 22 0.8 17 0.1 42.9 7.1 6.0 7.4 Example 66
6 22 0.8 16 0.1 42.9 7.1 6.0 8.3 Example 67 3 25 0.8 22 0.1 42.9
7.1 6.0 6.1 Comparative Example 15 3 27 0.8 24 0.1 42.9 7.1 6.0 6.4
Example 68 3 22 0.9 19 0.1 42.9 7.1 6.0 5.7 Example 69 3 22 1 19
0.1 42.9 7.1 6.0 5.7 Example 70 3 22 1.5 19 0.1 42.9 7.1 6.0 5.7
Comparative Example 16 3 22 1.6 19 0.1 42.9 7.1 6.0 5.7 Comparative
Example 17 3 7 0.1 4 0.1 42.9 7.1 6.0 3.6 Comparative 3 7 0.8 4 0.1
42.9 7.1 6.0 3.6 Example 18 Example 71 1.5 18 0.5 16.5 0.1 42.9 7.1
6.0 3.8 Example 72 1.5 18 0.5 16.5 0.05 42.9 7.1 6.0 3.8 Example 73
1.5 18 0.5 16.5 0 42.9 7.1 6.0 3.8 Example 74 1.5 18 0.5 16.5 0.5
42.9 7.1 6.0 3.8 Example 75 1.5 18 0.5 16.5 0.6 42.9 7.1 6.0 3.8
Example 76 1.5 18 0.5 16.5 0.1 38 12 3.2 5.5 Example 77 1.5 18 0.5
16.5 0.1 40 10 4.0 4.8 Example 78 1.5 18 0.5 16.5 0.1 44 6 7.3 3.5
Example 79 1.5 18 0.5 16.5 0.1 45.4 4.6 9.9 3.0 Example 80 1.5 18
0.5 16.5 0.1 46.3 3.7 12.5 2.7 Example 81 1.5 18 0.5 16.5 0.1 42.9
7.1 6.0 3.8 Example 82 1.5 18 0.5 16.5 0.1 42.9 7.1 6.0 3.8 Example
83 1.5 18 0.5 16.5 0.1 42.9 7.1 6.0 3.8 Example 84 1.5 18 0.5 16.5
0.1 42.9 7.1 6.0 3.8 Example 85 1.5 18 0.5 16.5 0.1 42.9 7.1 6.0
3.8
TABLE-US-00002 TABLE 2-1 Film property Back sheet property
Ultraviolet Light- Ultraviolet Light- Moist-heat Flame light
reflecting Moist-heat Flame light reflecting resistance retardancy
Curling resistance resistance property Flatness Adehesion
resistance retardancy resistance property Example 1 S S S S B S S S
S S B Example 2 S S S B B S S S S B B Example 3 S S S B B S S S S B
B Example 4 S S S C C S S S S C C Example 5 S S S D C S S S S D C
Example 6 S S S C B S S S S C B Comparative S S S E B S S S S E B
Example 1 Example 7 B S B S B B S B S S B Example 8 B S B S B B S B
S S B Example 9 C S C S B C S C S S B Comparative E S E S B E S E S
S B Example 2 Example 10 S S S S B S S S S S B Example 11 S S C B B
C S S S B B Example 12 S S C B B C S S S B B Example 13 S S C C B C
S S S C B Example 14 S S C D B C S S S D B Example 15 B S C S B C S
B S S B Example 16 D S D S B D S D S S B Comparative D S E S B E S
D S S B Example 3 Example 17 B S B S B B S B S S B Example 18 B S B
S B B S B S S B Example 19 C S C S B C S C S S B Comparative E S E
S B E S E S S B Example 4 Example 20 S S S S B S S S S S B Example
21 C S S S A S B C S S A Example 22 D S S S A S D D S S A Example
23 D S S S A S E D S S A Example 24 S S S C B S S S S C B
Comparative S S S E B S S S S E B Example 5 Example 25 B S B S B B
S B S S B Example 26 B S B S B B S B S S B Example 27 C S C S B C S
C S S B Comparative E S E S B E S E S S B Example 6 Example 28 S S
S S A S S S S S A Example 29 C S S S A S B C S S A Example 30 D S S
S A S D D S S A Example 31 D S S S A S E D S S A Example 32 A S B S
A B S A S S A Comparative B S E S B E S B S S B Example 7 Example
33 B S B S A B S B S S A Example 34 B S B S A B S B S S A Example
35 C S C S A C S C S S A Comparative E S E S A E S E S S A Example
8 Example 36 S S S S B S S S S S B Example 37 S S S B B S S S S B B
Example 38 S S S B B S S S S B B Example 39 S S S C C S S S S C C
Example 40 S S S D C S S S S D C Example 41 S S S C B S S S S C B
Comparative S S S E B S S S S E B Example 9 Example 42 S C S S B S
S S C S B Example 43 S C S S B S S S C S B Example 44 S D S S B S S
S D S B Comparative S E S S B S S S E S B Example 10 Example 45 S S
S S B S S S S S B Example 46 S S C A B C S S S A B Example 47 S S C
A B C S S S A B Example 48 S S C B B C S S S B B Example 49 S S C C
B C S S S C B Example 50 B S C S B C S B S S B Example 51 D S D S B
D S D S S B Comparative D S E S B E S D S S B Example 11 Example 52
S C S S B S S S C S B Example 53 S C S S B S S S C S B Example 54 S
D S S B S S S D S B Comparative S E S S B S S S E S B Example 12
Example 55 S S S S B S S S S S B Example 56 D S S S A S B D S S A
Example 57 D S S S A S D D S S A Example 58 D S S S A S E D S S A
Example 59 S S S C B S S S S C B Comparative S S S E B S S S S E B
Example 13 Example 60 S C S S B S S S C S B Example 61 S C S S B S
S S C S B Example 62 S D S S B S S S D S B Comparative S E S S B S
S S E S B Example 14 Example 63 S S S S A S S S S S A Example 64 C
S S S A S B C S S A Example 65 D S S S A S D D S S A Example 66 D S
S S A S E D S S A Example 67 A S C S A C S A S S A Comparative B S
E S A E S B S S A Example 15 Example 68 S C S S A S S S C S A
Example 69 S C S S A S S S C S A Example 70 S D S S A S S S D S A
Comparative S E S S A S S S E S A Example 16 Comparative S S S E B
S S S S E B Example 17 Comparative S S S E A S S S S E A Example 18
Example 71 S S S S B S S S S S B Example 72 S S S S B S S S S S B
Example 73 C S S S B S S C S S B Example 74 S S S S B S S S S S B
Example 75 S C S S B S S S C S B Example 76 S S B S B B S S S S B
Example 77 S S S S B S S S S S B Example 78 S S S S B S S S S S B
Example 79 S S S S B S S S S S B Example 80 S S S C B S S S S C B
Example 81 C S S S B S S C S S B Example 82 S A S B S S S S A B S
Example 83 S S S S B S E S S S B Example 84 A S S S B S S A S S B
Example 85 C S S S B S S C S S B
INDUSTRIAL APPLICABILITY
[0212] The polyester film is a polyester film which highly
satisfactorily combine high moisture-heat resistance, flame
retardancy, and other properties (in particular, ultraviolet light
resistance, light-reflecting properties, etc.) over a long period,
and it can be suitably used for applications including solar-cell
back sheets, sheet heating elements or electrical insulation
materials such as a flat cable, capacitor materials, automobile
materials and building material, which make use of its
characteristics.
* * * * *